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Full vulnerability report · 2026
CVE-2026-78058High confidence

Apache bRPC: Unbounded Resource Consumption and Crash in the HTTP/2 Receive Path

Apache Software Foundation · Apache bRPC

…UnscoredAssess manually
Recommended action
Needs assessment

No CVSS base score is available from the CNA, CISA ADP or NIST. Absence of a score is not evidence of low risk; review the vendor advisory, affected exposure and exploit evidence.

Fix not verified
R
Operational reassessment

Published severity in operational context

Open reassessment dashboard →
Published severityUnscoredOperational priority:Needs assessment, manual assessment needed.unscored

Evidence used

  • No CISA KEV confirmation is currently recorded.
  • EPSS is 0.31% for the current model date.

Compensating controls

  • Restrict local access and enforce least privilege on affected hosts.
  • Monitor vendor guidance and exploitation sources for a material change.

Verification

  1. Confirm that the asset runs Apache Software Foundation Apache bRPC and falls inside the recorded affected range.
  2. Recheck the vendor advisory before scheduling a change because no verified fixed version is currently retained.
  3. Validate exposure, authentication requirements and compensating controls in the actual environment.
  4. Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Mitigation target: Manual assessmentRemediation target: Manual assessment

This automated reassessment organises public evidence. It does not know asset exposure, business impact or control effectiveness and does not replace CVSS or a human risk decision.

Optional official sources

National CERT insights
?CERT means Computer Emergency Response Team; CSIRT is the closely related term Computer Security Incident Response Team.

Choose official national sources for this report. Each advisory shows its original language. Your selection is remembered on this device and included in shared links.

Official European source

ENISA European Vulnerability Database

Official EUVD identifiers, advisory evidence and known-exploited context. Missing fields are not treated as evidence of low risk.

1 current
ENISA EUVD identifier

EUVD-2026-107184

No EUVD known-exploited evidence

Uncontrolled resource consumption in the HTTP/2 (h2) receive path of Apache bRPC (version < 1.18.0) on all platforms allows a remote unauthenticated attacker to crash the server or grow its memory without bound by sending crafted HTTP/2 frames. Root Cause: The h2 parser, enabled by default on every bRPC server port and used by h2/gRPC clients, trusts the peer to respect receive-side limits that bRPC advertises but never enforces: 1. SETTINGS_MAX_CONCURRENT_STREAMS defaulted to unlimited and was never checked on the server, letting a peer pin an unbounded number of pending streams per connection (~100x memory amplification). 2. SETTINGS_MAX_HEADER_LIST_SIZE defaulted to unlimited and was never enforced; 1-byte HPACK indexed references amplify a small HEADERS frame ~4000x into an unbounded decoded header list ("HPACK bomb"), and a never-completed HEADERS/CONTINUATION block accumulates memory without limit. 3. Control-frame acks (PING/SETTINGS acks, RST_STREAM, GOAWAY, WINDOW_UPDATE) unconditionally bypassed the -socket_max_unwritten_bytes write cap, so a PING flood combined with withheld TCP reads grew the connection buffer without the documented bound. 4. The HPACK dynamic table size update was validated against the protocol default (4096) instead of the advertised SETTINGS_HEADER_TABLE_SIZE, which together with the dynamic-table queue/accounting issue can desynchronize the decoder and dereference NULL (crash). Affected scenarios: Any bRPC server serving HTTP/h2/gRPC to an untrusted network, and any bRPC h2/gRPC client connecting to an untrusted backend. The h2 parser runs before any Authenticator check on the shared port. How to fix: Upgrade bRPC, or apply the patch in https://github.com/apache/brpc/pull/3474. Note: After applying the fix the following limits are enforced by default: - max_concurrent_streams: 1024 per connection (4294967295 restores unlimited). - max_header_list_size: 1 MiB decoded size per stream (4294967295 restores unlimited; -h2_client_max_header_list_size for clients). - h2 control-frame acks respect -socket_max_unwritten_bytes (-h2_ack_ignore_eovercrowded restores the old behavior). Requests exceeding these limits are rejected (RST_STREAM(REFUSED_STREAM) or a connection error).

EUVD state
Present in the current official mapping
Known exploitation
Not present in the current ENISA EUVD known-exploited dataset. This is not proof of no exploitation.
ENISA score
0.0
Advisory evidence
No linked advisory details stored yet
Recommended actionNeeds assessment

No CVSS base score is available from the CNA, CISA ADP or NIST. Absence of a score is not evidence of low risk; review the vendor advisory, affected exposure and exploit evidence.

Fix not verified
01

What, why and how

Uncontrolled resource consumption in the HTTP/2 (h2) receive path of Apache bRPC (version < 1.18.0) on all platforms allows a remote unauthenticated attacker to crash the server or grow its memory without bound by sending crafted HTTP/2 frames. Root Cause: The h2 parser, enabled by default on every bRPC server port and used by h2/gRPC clients, trusts the peer to respect receive-side limits that bRPC advertises but never enforces: 1. SETTINGS_MAX_CONCURRENT_STREAMS defaulted to unlimited and was never checked on the server, letting a peer pin an unbounded number of pending streams per connection (~100x memory amplification). 2. SETTINGS_MAX_HEADER_LIST_SIZE defaulted to unlimited and was never enforced; 1-byte HPACK indexed references amplify a small HEADERS frame ~4000x into an unbounded decoded header list ("HPACK bomb"), and a never-completed HEADERS/CONTINUATION block accumulates memory without limit. 3. Control-frame acks (PING/SETTINGS acks, RST_STREAM, GOAWAY, WINDOW_UPDATE) unconditionally bypassed the -socket_max_unwritten_bytes write cap, so a PING flood combined with withheld TCP reads grew the connection buffer without the documented bound. 4. The HPACK dynamic table size update was validated against the protocol default (4096) instead of the advertised SETTINGS_HEADER_TABLE_SIZE, which together with the dynamic-table queue/accounting issue can desynchronize the decoder and dereference NULL (crash). Affected scenarios: Any bRPC server serving HTTP/h2/gRPC to an untrusted network, and any bRPC h2/gRPC client connecting to an untrusted backend. The h2 parser runs before any Authenticator check on the shared port. How to fix: Upgrade bRPC, or apply the patch in https://github.com/apache/brpc/pull/3474. Note: After applying the fix the following limits are enforced by default: - max_concurrent_streams: 1024 per connection (4294967295 restores unlimited). - max_header_list_size: 1 MiB decoded size per stream (4294967295 restores unlimited; -h2_client_max_header_list_size for clients). - h2 control-frame acks respect -socket_max_unwritten_bytes (-h2_ack_ignore_eovercrowded restores the old behavior). Requests exceeding these limits are rejected (RST_STREAM(REFUSED_STREAM) or a connection error).

What

Uncontrolled resource consumption in the HTTP/2 (h2) receive path of Apache bRPC (version < 1.18.0) on all platforms allows a remote unauthenticated attacker to crash the server or grow its memory without bound by sending crafted HTTP/2 frames. Root Cause: The h2 parser, enabled by default on every bRPC server port and used by h2/gRPC clients, trusts the peer to respect receive-side limits that bRPC advertises but never enforces: 1. SETTINGS_MAX_CONCURRENT_STREAMS defaulted to unlimited and was never checked on the server, letting a peer pin an unbounded number of pending streams per connection (~100x memory amplification). 2. SETTINGS_MAX_HEADER_LIST_SIZE defaulted to unlimited and was never enforced; 1-byte HPACK indexed references amplify a small HEADERS frame ~4000x into an unbounded decoded header list ("HPACK bomb"), and a never-completed HEADERS/CONTINUATION block accumulates memory without limit. 3. Control-frame acks (PING/SETTINGS acks, RST_STREAM, GOAWAY, WINDOW_UPDATE) unconditionally bypassed the -socket_max_unwritten_bytes write cap, so a PING flood combined with withheld TCP reads grew the connection buffer without the documented bound. 4. The HPACK dynamic table size update was validated against the protocol default (4096) instead of the advertised SETTINGS_HEADER_TABLE_SIZE, which together with the dynamic-table queue/accounting issue can desynchronize the decoder and dereference NULL (crash). Affected scenarios: Any bRPC server serving HTTP/h2/gRPC to an untrusted network, and any bRPC h2/gRPC client connecting to an untrusted backend. The h2 parser runs before any Authenticator check on the shared port. How to fix: Upgrade bRPC, or apply the patch in https://github.com/apache/brpc/pull/3474. Note: After applying the fix the following limits are enforced by default: - max_concurrent_streams: 1024 per connection (4294967295 restores unlimited). - max_header_list_size: 1 MiB decoded size per stream (4294967295 restores unlimited; -h2_client_max_header_list_size for clients). - h2 control-frame acks respect -socket_max_unwritten_bytes (-h2_ack_ignore_eovercrowded restores the old behavior). Requests exceeding these limits are rejected (RST_STREAM(REFUSED_STREAM) or a connection error).

Why

The product does not properly control the allocation and maintenance of a limited resource.

How

An attacker operating through the affected interface may attempt exploitation when the stated preconditions are met. If successful, the issue may disrupt the affected service.

What

Uncontrolled resource consumption in the HTTP/2 (h2) receive path of Apache bRPC (version < 1.18.0) on all platforms allows a remote unauthenticated attacker to crash the server or grow its memory without bound by sending crafted HTTP/2 frames. Root Cause: The h2 parser, enabled by default on every bRPC server port and used by h2/gRPC clients, trusts the peer to respect receive-side limits that bRPC advertises but never enforces: 1. SETTINGS_MAX_CONCURRENT_STREAMS defaulted to unlimited and was never checked on the server, letting a peer pin an unbounded number of pending streams per connection (~100x memory amplification). 2. SETTINGS_MAX_HEADER_LIST_SIZE defaulted to unlimited and was never enforced; 1-byte HPACK indexed references amplify a small HEADERS frame ~4000x into an unbounded decoded header list ("HPACK bomb"), and a never-completed HEADERS/CONTINUATION block accumulates memory without limit. 3. Control-frame acks (PING/SETTINGS acks, RST_STREAM, GOAWAY, WINDOW_UPDATE) unconditionally bypassed the -socket_max_unwritten_bytes write cap, so a PING flood combined with withheld TCP reads grew the connection buffer without the documented bound. 4. The HPACK dynamic table size update was validated against the protocol default (4096) instead of the advertised SETTINGS_HEADER_TABLE_SIZE, which together with the dynamic-table queue/accounting issue can desynchronize the decoder and dereference NULL (crash). Affected scenarios: Any bRPC server serving HTTP/h2/gRPC to an untrusted network, and any bRPC h2/gRPC client connecting to an untrusted backend. The h2 parser runs before any Authenticator check on the shared port. How to fix: Upgrade bRPC, or apply the patch in https://github.com/apache/brpc/pull/3474. Note: After applying the fix the following limits are enforced by default: - max_concurrent_streams: 1024 per connection (4294967295 restores unlimited). - max_header_list_size: 1 MiB decoded size per stream (4294967295 restores unlimited; -h2_client_max_header_list_size for clients). - h2 control-frame acks respect -socket_max_unwritten_bytes (-h2_ack_ignore_eovercrowded restores the old behavior). Requests exceeding these limits are rejected (RST_STREAM(REFUSED_STREAM) or a connection error).

Why

The product does not properly control the allocation and maintenance of a limited resource.

How

An attacker operating through the affected interface may attempt exploitation when the stated preconditions are met. If successful, the issue may disrupt the affected service.

02

Exploit reality and attack path

CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.

Observed exploitation
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
No confirmed evidence

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
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
None recorded

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
the affected interface → Uncontrolled Resource Consumption → disrupt the affected service
Attack surface
Unspecified
Privileges required
Not stated in the selected CVSS metric
User interaction
Not stated in the selected CVSS metric
Attack complexity
Not stated in the selected CVSS metric
Security boundary
Not stated in the selected CVSS metric
Weakness
?CWE means Common Weakness Enumeration: a standard category for the underlying weakness.
CWE-400 ↗

CWE-400: Uncontrolled Resource Consumption. The product does not properly control the allocation and maintenance of a limited resource.

CVSS vector
?CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.
Not available from the selected scoring authority.
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.
Denial of serviceCWE-400
A

Official authority intelligence

Only matched European and national findings are included. Language selectors and unavailable sources are omitted.

ENISA EUVD · EUVD-2026-107184Official EUVD mapping

Uncontrolled resource consumption in the HTTP/2 (h2) receive path of Apache bRPC (version < 1.18.0) on all platforms allows a remote unauthenticated attacker to crash the server or grow its memory without bound by sending crafted HTTP/2 frames. Root Cause: The h2 parser, enabled by default on every bRPC server port and used by h2/gRPC clients, trusts the peer to respect receive-side limits that bRPC advertises but never enforces: 1. SETTINGS_MAX_CONCURRENT_STREAMS defaulted to unlimited and was never checked on the server, letting a peer pin an unbounded number of pending streams per connection (~100x memory amplification). 2. SETTINGS_MAX_HEADER_LIST_SIZE defaulted to unlimited and was never enforced; 1-byte HPACK indexed references amplify a small HEADERS frame ~4000x into an unbounded decoded header list ("HPACK bomb"), and a never-completed HEADERS/CONTINUATION block accumulates memory without limit. 3. Control-frame acks (PING/SETTINGS acks, RST_STREAM, GOAWAY, WINDOW_UPDATE) unconditionally bypassed the -socket_max_unwritten_bytes write cap, so a PING flood combined with withheld TCP reads grew the connection buffer without the documented bound. 4. The HPACK dynamic table size update was validated against the protocol default (4096) instead of the advertised SETTINGS_HEADER_TABLE_SIZE, which together with the dynamic-table queue/accounting issue can desynchronize the decoder and dereference NULL (crash). Affected scenarios: Any bRPC server serving HTTP/h2/gRPC to an untrusted network, and any bRPC h2/gRPC client connecting to an untrusted backend. The h2 parser runs before any Authenticator check on the shared port. How to fix: Upgrade bRPC, or apply the patch in https://github.com/apache/brpc/pull/3474. Note: After applying the fix the following limits are enforced by default: - max_concurrent_streams: 1024 per connection (4294967295 restores unlimited). - max_header_list_size: 1 MiB decoded size per stream (4294967295 restores unlimited; -h2_client_max_header_list_size for clients). - h2 control-frame acks respect -socket_max_unwritten_bytes (-h2_ack_ignore_eovercrowded restores the old behavior). Requests exceeding these limits are rejected (RST_STREAM(REFUSED_STREAM) or a connection error).

Official EUVD record ↗
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 not verified
Affected
Apache bRPC: < 1.18.0
Fixed
No fixed version is explicitly recorded in the structured CVE data.
Action
No verified patch reference is present in the current structured sources. Check the vendor advisory before making a change.
Workaround
No verified workaround is recorded. Limit untrusted access and use least privilege until authoritative guidance is available.
04

Evidence and provenance

Published 21 Oct 2026 · Last source change 21 Oct 2026, 11:52 UTC · CWE-400 · Uncontrolled Resource Consumption

CVE recordCVE.org · 5.2
CVSS sourceUnavailable
EPSS source
?The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.
FIRST · tracked since 2026-10-22
European sourceENISA EUVD · EUVD-2026-107184
Product sourceCNA
Remediation sourceCVE/CNA references
CWE sourceCNA
NVD statusNVD not scheduled

Missing structured fields: CVSS base score. Missing data is not evidence of low risk; review the primary advisory.

Material change intelligence

What changed after publication

View recent updates ↗
  1. ENISA EUVD mappingEUVD-2026-107184 was added to the official ENISA EUVD mapping for this CVE.
    Before
    not recorded
    After
    {"euvdId":"EUVD-2026-107184"}
    ENISA EUVD ↗
  2. Vendor guidanceAuthoritative vendor guidance changed: removed vendor advisory: lists.apache.org/2pf15ojj0vr7rtx95677kgtl1mx3gdgb.
    Before
    vendor advisory: lists.apache.org/2pf15ojj0vr7rtx95677kgtl1mx3gdgb
    After
    no authoritative guidance recorded
    CNA ↗
  3. Catalogue recordCVE added to the BlackTree catalogue.
    CNA ↗
Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
ENISA EUVD · EUVD-2026-107184↗CVE authority or vendor reference↗Official CVE record (CNA and ADP data)↗NVD record↗
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.
Free version - for non-commercial use only.CVE-2026-78058 · cve.blacktree.nl