Evidence used
- No CISA KEV confirmation is currently recorded.
- The selected CVSS metric records a network-reachable, unauthenticated path with no user interaction.
- EPSS is 0.48% for the current model date.
BlackTreeCVE IntelligenceFull vulnerability report · 2023
CVE-2023-33953High confidence
Denial-of-Service in gRPC
Google · gRPC
7.5HighCVSS 3.1
Patch only the product branches with a verified fix
Fix availability varies by productHigh technical severity; prioritise exposed affected systems while verifying vendor guidance. Verified remediation exists for at least one product or source, but 11 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.
R
Open reassessment dashboard →Operational reassessment
Published severity in operational context
Published severityHigh→Operational priority:High, unchanged from published severity.unchanged
Compensating controls
- Validate the affected product branch and deploy the verified fixed release.
- Restrict the affected network interface to trusted sources where business-safe.
- Monitor vendor guidance and exploitation sources for a material change.
Verification
- Confirm that the asset runs Google gRPC and falls inside the recorded affected range.
- Verify the installed build against the product-specific fixed version after deployment.
- Validate exposure, authentication requirements and compensating controls in the actual environment.
- Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Remediation availability differs by product scope
Verified remediation exists for at least one product or source, but 11 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.
- Siemens ProductCERT: 7 affected or under-investigation product states without a fixed product state in the same current advisory
- Debian Security Tracker: 4 affected package states with no published fix
Distribution package intelligence
5 package statesRelease-specific package status
Debian, ubuntu findings are scoped to the named distribution, release and source package. An absent finding does not mean a package is unaffected.
Package result overrides the generic status
BlackTree has verified remediation for at least one product or source, but the relevant distribution still reports no fixed package for 4 affected package states shown here. Treat those rows as affected with no fix until that distribution publishes a fixed version.
Repository candidate not checked
A published vendor fix does not prove that a matching update is enabled and installable on a particular asset. Confirm the local package candidate before scheduling remediation.
| Distribution release | Source package | Vendor state | Fixed version | Evidence |
|---|---|---|---|---|
| Debian trixietrixie · source | grpc | Affected, no fix publishedDebian currently tracks this release as open. | Not published in this feed | Debian Security Tracker ↗Source updated 5 Oct 2026 |
| Debian bookwormbookworm · source | grpc | Affected, no fix publishedDebian currently tracks this release as open. | Not published in this feed | Debian Security Tracker ↗Source updated 5 Oct 2026 |
| Debian forkyforky · source | grpc | Affected, no fix publishedDebian currently tracks this release as open. | Not published in this feed | Debian Security Tracker ↗Source updated 5 Oct 2026 |
| Debian sidsid · source | grpc | Affected, no fix publishedDebian currently tracks this release as open. | Not published in this feed | Debian Security Tracker ↗Source updated 5 Oct 2026 |
| Ubuntu 24.04 LTSnoble · standard archive | grpc | Under evaluationCanonical reports that the package might be affected and still needs evaluation or fixing. | Not published in this feed | Canonical Ubuntu Security ↗Source updated 5 Oct 2026 |
Open-source package ranges8 source-attributed ranges
These OSV and GitHub advisory ranges apply only to the named package and ecosystem. A listed fixed version is not a universal product patch or proof that an update is installed.
| Ecosystem and package | Affected range | First fixed version | Evidence |
|---|---|---|---|
| PyPIgrpcio | ECOSYSTEM: introduced 0; fixed 1.53.2 | 1.53.2 | OSV record ↗aggregator derived · 7 Jul 2026 |
| PyPIgrpcio | ECOSYSTEM: introduced 1.54.0; fixed 1.54.3 | 1.54.3 | OSV record ↗aggregator derived · 7 Jul 2026 |
| PyPIgrpcio | ECOSYSTEM: introduced 1.55.0; fixed 1.55.2 | 1.55.2 | OSV record ↗aggregator derived · 7 Jul 2026 |
| PyPIgrpcio | ECOSYSTEM: introduced 1.56.0; fixed 1.56.2 | 1.56.2 | OSV record ↗aggregator derived · 7 Jul 2026 |
| RubyGemsgrpc | ECOSYSTEM: introduced 0; fixed 1.53.2 | 1.53.2 | OSV record ↗aggregator derived · 7 Jul 2026 |
| RubyGemsgrpc | ECOSYSTEM: introduced 1.54.0; fixed 1.54.3 | 1.54.3 | OSV record ↗aggregator derived · 7 Jul 2026 |
| RubyGemsgrpc | ECOSYSTEM: introduced 1.55.0; fixed 1.55.2 | 1.55.2 | OSV record ↗aggregator derived · 7 Jul 2026 |
| RubyGemsgrpc | ECOSYSTEM: introduced 1.56.0; fixed 1.56.2 | 1.56.2 | OSV record ↗aggregator derived · 7 Jul 2026 |
Direct vendor intelligence
2 currentAuthoritative vendor CSAF and VEX advisories
Structured product status and remediation from the issuing vendor. Product-state explanations are always visible; large lists can be searched or downloaded.
CVE-2023-33953 · CSAF 2.0 · revision 3 · status not statedRed Hat Product SecuritygRPC: hpack table accounting errors can lead to denial of service
The vendor explicitly identifies these products or versions as containing the fix.
- rhc-worker-playbook-0:0.1.10-1.el9_5.aarch64 as a component of Red Hat Enterprise Linux AppStream (v. 9)
- rhc-worker-playbook-0:0.1.10-1.el9_5.ppc64le as a component of Red Hat Enterprise Linux AppStream (v. 9)
- rhc-worker-playbook-0:0.1.10-1.el9_5.s390x as a component of Red Hat Enterprise Linux AppStream (v. 9)
- rhc-worker-playbook-0:0.1.10-1.el9_5.src as a component of Red Hat Enterprise Linux AppStream (v. 9)
- rhc-worker-playbook-0:0.1.10-1.el9_5.x86_64 as a component of Red Hat Enterprise Linux AppStream (v. 9)
- rhc-worker-playbook-debuginfo-0:0.1.10-1.el9_5.aarch64 as a component of Red Hat Enterprise Linux AppStream (v. 9)
- rhc-worker-playbook-debuginfo-0:0.1.10-1.el9_5.ppc64le as a component of Red Hat Enterprise Linux AppStream (v. 9)
- rhc-worker-playbook-debuginfo-0:0.1.10-1.el9_5.s390x as a component of Red Hat Enterprise Linux AppStream (v. 9)
- rhc-worker-playbook-debuginfo-0:0.1.10-1.el9_5.x86_64 as a component of Red Hat Enterprise Linux AppStream (v. 9)
- Summary
- A flaw was found in the gRPC lib. This vulnerability allows hpack table accounting errors that could lead to unwanted disconnects between clients and servers in exceptional cases. This issue leads to Unbounded memory buffering in the HPACK parser and Unbounded CPU consumption in the HPACK parser.
- Remediation
- For details on how to apply this update, which includes the changes described in this advisory, refer to: https://access.redhat.com/articles/11258
SSA-093430 · CSAF 2.0 · revision 2 · interimSiemens ProductCERTSSA-093430: Multiple Vulnerabilities in SIMATIC RTLS Locating Manager before V3.0
The vendor explicitly identifies these products as affected by this CVE.
- SIMATIC RTLS Locating Manager (6GT2780-0DA00)
- SIMATIC RTLS Locating Manager (6GT2780-0DA10)
- SIMATIC RTLS Locating Manager (6GT2780-0DA20)
- SIMATIC RTLS Locating Manager (6GT2780-0DA30)
- SIMATIC RTLS Locating Manager (6GT2780-1EA10)
- SIMATIC RTLS Locating Manager (6GT2780-1EA20)
- SIMATIC RTLS Locating Manager (6GT2780-1EA30)
- Summary
- PC contains a vulnerability that allows hpack table accounting errors could lead to unwanted disconnects between clients and servers in exceptional cases. Three vectors were found that allow the following DOS attacks: - Unbounded memory buffering in the HPACK parser - Unbounded CPU consumption in the HPACK parser The unbounded CPU consumption is down to a copy that occurred per-input-block in the parser, and because that could be unbounded due to the memory copy bug we end up with a parsing loop, with n selected by the client. The unbounded memory buffering bugs: - The header size limit check was behind the string reading code, so we needed to first buffer up to a 4 gigabyte string before rejecting it as longer than 8 or 16kb. - HPACK varints have an encoding quirk whereby an infinite number of 0’s can be added at the start of an integer. gRPC’s hpack parser needed to read all of them before concluding a parse. - gRPC’s metadata overflow check was performed per frame, so that the following sequence of frames could cause infinite buffering: HEADERS: containing a: 1 CONTINUATION: containing a: 2 CONTINUATION: containing a: 3 etc… - Unbounded memory buffering in the HPACK parser - Unbounded CPU consumption in the HPACK parser The unbounded CPU consumption is down to a copy that occurred per-input-block in the parser, and because that could be unbounded due to the memory copy bug we end up with an parsing loop, with n selected by the client. The unbounded memory buffering bugs: - The header size limit check was behind the string reading code, so we needed to first buffer up to a 4 gigabyte string before rejecting it as longer than 8 or 16kb. - HPACK varints have an encoding quirk whereby an infinite number of 0’s can be added at the start of an integer. gRPC’s hpack parser needed to read all of them before concluding a parse. - gRPC’s metadata overflow check was performed per frame, so that the following sequence of frames could cause infinite buffering: HEADERS: containing a: 1 CONTINUATION: containing a: 2 CONTINUATION: containing a: 3 etc…
- Remediation
- Update to V3.0.1.1 or later version The update is available from Siemens Online Software Delivery (OSD).
High technical severity; prioritise exposed affected systems while verifying vendor guidance. Verified remediation exists for at least one product or source, but 11 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.
Fix availability varies by product01
What, why and how
gRPC contains a vulnerability that allows hpack table accounting errors could lead to unwanted disconnects between clients and servers in exceptional cases/ Three vectors were found that allow the following DOS attacks: - Unbounded memory buffering in the HPACK parser - Unbounded CPU consumption in the HPACK parser The unbounded CPU consumption is down to a copy that occurred per-input-block in the parser, and because that could be unbounded due to the memory copy bug we end up with an O(n^2) parsing loop, with n selected by the client. The unbounded memory buffering bugs: - The header size limit check was behind the string reading code, so we needed to first buffer up to a 4 gigabyte string before rejecting it as longer than 8 or 16kb. - HPACK varints have an encoding quirk whereby an infinite number of 0’s can be added at the start of an integer. gRPC’s hpack parser needed to read all of them before concluding a parse. - gRPC’s metadata overflow check was performed per frame, so that the following sequence of frames could cause infinite buffering: HEADERS: containing a: 1 CONTINUATION: containing a: 2 CONTINUATION: containing a: 3 etc…
What
gRPC contains a vulnerability that allows hpack table accounting errors could lead to unwanted disconnects between clients and servers in exceptional cases/ Three vectors were found that allow the following DOS attacks: - Unbounded memory buffering in the HPACK parser - Unbounded CPU consumption in the HPACK parser The unbounded CPU consumption is down to a copy that occurred per-input-block in the parser, and because that could be unbounded due to the memory copy bug we end up with an O(n^2) parsing loop, with n selected by the client. The unbounded memory buffering bugs: - The header size limit check was behind the string reading code, so we needed to first buffer up to a 4 gigabyte string before rejecting it as longer than 8 or 16kb. - HPACK varints have an encoding quirk whereby an infinite number of 0’s can be added at the start of an integer. gRPC’s hpack parser needed to read all of them before concluding a parse. - gRPC’s metadata overflow check was performed per frame, so that the following sequence of frames could cause infinite buffering: HEADERS: containing a: 1 CONTINUATION: containing a: 2 CONTINUATION: containing a: 3 etc…
Why
The product performs an iteration or loop without sufficiently limiting the number of times that the loop is executed.
How
An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.
What
gRPC contains a vulnerability that allows hpack table accounting errors could lead to unwanted disconnects between clients and servers in exceptional cases/ Three vectors were found that allow the following DOS attacks: - Unbounded memory buffering in the HPACK parser - Unbounded CPU consumption in the HPACK parser The unbounded CPU consumption is down to a copy that occurred per-input-block in the parser, and because that could be unbounded due to the memory copy bug we end up with an O(n^2) parsing loop, with n selected by the client. The unbounded memory buffering bugs: - The header size limit check was behind the string reading code, so we needed to first buffer up to a 4 gigabyte string before rejecting it as longer than 8 or 16kb. - HPACK varints have an encoding quirk whereby an infinite number of 0’s can be added at the start of an integer. gRPC’s hpack parser needed to read all of them before concluding a parse. - gRPC’s metadata overflow check was performed per frame, so that the following sequence of frames could cause infinite buffering: HEADERS: containing a: 1 CONTINUATION: containing a: 2 CONTINUATION: containing a: 3 etc…
Why
The product performs an iteration or loop without sufficiently limiting the number of times that the loop is executed.
How
An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.
02
Exploit reality and attack path
CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.
Observed exploitation No confirmed evidence
?
Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.
Public PoC / exploit material None recorded
?
Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.No exploit-tagged reference or CISA SSVC proof-of-concept state is currently recorded. Research may still exist outside the structured feeds.
- Likely attack path
- a network path → Excessive Iteration → cause the confidentiality, integrity or availability impact described by the vendor
- Attack surface
- Network
- Privileges required
- None: unauthenticated exploitation is possible
- User interaction
- None
- Attack complexity
- Low: no specialised conditions are recorded
- Security boundary
- Unchanged: impact remains within the vulnerable component's security authority
- Weakness
?
CWE means Common Weakness Enumeration: a standard category for the underlying weakness. - CWE-834 ↗
CWE-834: Excessive Iteration. The product performs an iteration or loop without sufficiently limiting the number of times that the loop is executed.
- CVSS vector
?
CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity. CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:HCommon Vulnerability Scoring System 3.1: the compact vector below is decoded into plain language.
AVNetworkAttack vector: The vulnerable component can be reached over a network.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.PRNonePrivileges required: The attacker does not need an account or existing privileges.UINoneUser interaction: No action by another user is required.SUnchangedScope: The security impact remains within the vulnerable component's authority.CNoneConfidentiality impact: No direct loss is represented by this metric.INoneIntegrity impact: No direct loss is represented by this metric.AHighAvailability impact: A successful attack can cause a major loss.- Post-exploitation / living off the land
- No specific living-off-the-land technique is confirmed in the structured sources. Monitor normal administration tools for activity inconsistent with the affected service's baseline.
03
Patch and workaround
Operational remediation based on structured source evidence.
- Status
?
Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change. - Fix availability varies by product
- Affected
- gRPC: < 1.56.1
- Fixed
- rhc-worker-playbook-0:0.1.10-1.el9_5.aarch64 as a component of Red Hat Enterprise Linux AppStream (v. 9)
- rhc-worker-playbook-0:0.1.10-1.el9_5.ppc64le as a component of Red Hat Enterprise Linux AppStream (v. 9)
- rhc-worker-playbook-0:0.1.10-1.el9_5.s390x as a component of Red Hat Enterprise Linux AppStream (v. 9)
- rhc-worker-playbook-0:0.1.10-1.el9_5.src as a component of Red Hat Enterprise Linux AppStream (v. 9)
- rhc-worker-playbook-0:0.1.10-1.el9_5.x86_64 as a component of Red Hat Enterprise Linux AppStream (v. 9)
- rhc-worker-playbook-debuginfo-0:0.1.10-1.el9_5.aarch64 as a component of Red Hat Enterprise Linux AppStream (v. 9)
- rhc-worker-playbook-debuginfo-0:0.1.10-1.el9_5.ppc64le as a component of Red Hat Enterprise Linux AppStream (v. 9)
- rhc-worker-playbook-debuginfo-0:0.1.10-1.el9_5.s390x as a component of Red Hat Enterprise Linux AppStream (v. 9)
- rhc-worker-playbook-debuginfo-0:0.1.10-1.el9_5.x86_64 as a component of Red Hat Enterprise Linux AppStream (v. 9)
- Action
- Use the product-specific evidence above. Patch only products with a verified fixed release, and keep every affected or under-investigation state without a matching fix in the remediation queue.
- Workaround
- No verified workaround is recorded. If business-safe, reduce exposure to the affected interface and allow only trusted sources until authoritative guidance is available.
04
Evidence and provenance
Published 9 Aug 2023 · Last source change 27 Sept 2024, 18:40 UTC · CWE-834 · Excessive Iteration
CVE recordCVE.org · 5.1
CVSS sourceCNA
EPSS source FIRST · tracked since 2026-08-14
?
The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.European sourceENISA EUVD · EUVD-2023-2204
Product sourceCNA
Remediation sourceVendor CSAF · Red Hat Product Security
CWE sourceCNA
NVD statusNVD modified after enrichment
Core structured fields are present and their contributing authorities are shown above.
Material change intelligence
View recent updates ↗What changed after publication
- Affected versionsThe structured affected or fixed version information changed.Red Hat Product Security ↗
- Before
- < 1.56.1 · Fixed: No fixed version is explicitly recorded in the structured CVE data.
- After
- < 1.56.1 · Fixed: For details on how to apply this update, which includes the changes described in this advisory, refer to: https://access.redhat.com/articles/11258
- Remediation statusRemediation status changed from Awaiting fix to Patch available.Red Hat Product Security ↗
- Before
- Awaiting fix
- After
- Patch available
CVE published
Fixed release recorded from official guidance
Technical terms and abbreviations used in this report
- CVE
- Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
- CVSS
- Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
- EPSS
- Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
- CWE
- Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
- CNA
- CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
- CISA ADP
- Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
- NVD
- National Vulnerability Database: NIST's enrichment service for CVE records.
- CERT / CSIRT
- A computer security incident response team that publishes warnings or coordinates incident response.
- PoC
- Proof of concept: public material that demonstrates or helps reproduce exploitation.
- CSAF
- Common Security Advisory Framework: a machine-readable format for security advisories.
- LoTL
- Living off the land: abuse of legitimate tools or system functions during an attack.