zipfile: bzip2/LZMA/Zstandard members decompress without a max_length bound, defeating chunked-read memory limits
Python Software Foundation · CPython
2.1LowCVSS 4.0
Recommended action
Scheduled
Low technical severity with no CISA KEV confirmation; remediate through the normal risk-based patch cycle unless local exposure raises the priority.
Patch available
Distribution package intelligence
Ubuntu vendor package status
Canonical’s release and source-package findings are shown separately from local repository availability.
1 package state
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.
Ubuntu release
Source package
Vendor state
Fixed version
Evidence
Ubuntu 24.04 LTSnoble · standard archive
python3.12
Under evaluationCanonical reports that the package might be affected and still needs evaluation or fixing.
National CERT insights ?CERT means Computer Emergency Response Team; CSIRT is the closely related term Computer Security Incident Response Team.
Select the national-authority views to include. The exact source language is shown on each matched advisory. Your choice is remembered on this device and encoded in the shareable URL.
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-2026-65519
No EUVD known-exploited evidence
When decompressing crafted zip files using the bzip/LZMA/Zstandard
compressions, Python could use an attacker-controlled size to
pre-allocate memory, possibly resulting in memory exhaustion.
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
2.1 · CVSS 4.0
Advisory evidence
No linked advisory details stored yet
Recommended actionScheduled
Low technical severity with no CISA KEV confirmation; remediate through the normal risk-based patch cycle unless local exposure raises the priority.
Patch available
01
What, why and how
When decompressing crafted zip files using the bzip/LZMA/Zstandard
compressions, Python could use an attacker-controlled size to
pre-allocate memory, possibly resulting in memory exhaustion.
What
When decompressing crafted zip files using the bzip/LZMA/Zstandard
compressions, Python could use an attacker-controlled size to
pre-allocate memory, possibly resulting in memory exhaustion.
Why
The product does not properly control the allocation and maintenance of a limited resource.
How
An attacker operating through a network path may attempt exploitation when the stated preconditions are met. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.
What
When decompressing crafted zip files using the bzip/LZMA/Zstandard
compressions, Python could use an attacker-controlled size to
pre-allocate memory, possibly resulting in memory exhaustion.
Why
The product does not properly control the allocation and maintenance of a limited resource.
How
An attacker operating through a network path may attempt exploitation when the stated preconditions are met. 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 ?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
a network path → Uncontrolled Resource Consumption → cause the confidentiality, integrity or availability impact described by the vendor
Attack surface
Network
Privileges required
None: unauthenticated exploitation is possible
User interaction
Active interaction required
Attack complexity
Low: no specialised conditions are recorded
Security boundary
Not a CVSS 4.0 base metric
Weakness ?CWE means Common Weakness Enumeration: a standard category for the underlying weakness.
Common Vulnerability Scoring System 4.0: 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.ATPresentAttack requirements: A particular deployment or execution condition must be present.PRNonePrivileges required: The attacker does not need an account or existing privileges.UIActiveUser interaction: A user must take a deliberate action for exploitation to succeed.VCNoneVulnerable-system confidentiality: No direct loss is represented by this metric.VINoneVulnerable-system integrity: No direct loss is represented by this metric.VALowVulnerable-system availability: A successful attack can cause a limited loss.SCNoneSubsequent-system confidentiality: No direct loss is represented by this metric.SINoneSubsequent-system integrity: No direct loss is represented by this metric.SANoneSubsequent-system availability: No direct loss is represented by this metric.
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.
NetworkUnauthenticatedCWE-400
A
Official authority intelligence
Only matched European and national findings are included. Language selectors and unavailable sources are omitted.
ENISA EUVD · EUVD-2026-65519Official EUVD mapping
When decompressing crafted zip files using the bzip/LZMA/Zstandard
compressions, Python could use an attacker-controlled size to
pre-allocate memory, possibly resulting in memory exhaustion.
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.
Review the linked authoritative reference and apply the recorded fixed release appropriate to the affected product branch.
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 25 Aug 2026 · Last source change 26 Aug 2026, 00:20 UTC · CWE-400 · Uncontrolled Resource Consumption
CVE recordCVE.org · 5.2
CVSS sourceCNA
EPSS source ?The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.FIRST · tracked since 2026-08-26
European sourceENISA EUVD · EUVD-2026-65519
Product sourceCNA
Remediation sourceCVE/CNA references
CWE sourceCNA
NVD statusNVD awaiting enrichment
Core structured fields are present and their contributing authorities are shown above.
Affected versionsThe structured affected or fixed version information changed.
Before
< 3.15.0rc2 · Fixed: An authoritative update reference is available, but the fixed version is not recorded in the structured CVE fields. Check the linked vendor advisory for the applicable release.
After
< 3.15.0rc2 · Fixed: No fixed version is explicitly recorded in the structured CVE data.
Affected versionsThe structured affected or fixed version information changed.
Before
< 3.15.0rc2 · Fixed: No fixed version is explicitly recorded in the structured CVE data.
After
< 3.15.0rc2 · Fixed: An authoritative update reference is available, but the fixed version is not recorded in the structured CVE fields. Check the linked vendor advisory for the applicable release.
Affected versionsThe structured affected or fixed version information changed.
Before
< 3.15.0 · Fixed: An authoritative update reference is available, but the fixed version is not recorded in the structured CVE fields. Check the linked vendor advisory for the applicable release.
After
< 3.15.0 · Fixed: No fixed version is explicitly recorded in the structured CVE data.
Affected versionsThe structured affected or fixed version information changed.
Before
< 3.15.0 · Fixed: No fixed version is explicitly recorded in the structured CVE data.
After
< 3.15.0 · Fixed: An authoritative update reference is available, but the fixed version is not recorded in the structured CVE fields. Check the linked vendor advisory for the applicable release.
Affected versionsThe structured affected or fixed version information changed.
Before
< 3.15.0 · Fixed: An authoritative update reference is available, but the fixed version is not recorded in the structured CVE fields. Check the linked vendor advisory for the applicable release.
After
< 3.15.0 · Fixed: No fixed version is explicitly recorded in the structured CVE data.
Affected versionsThe structured affected or fixed version information changed.
Before
< 3.16.0 · Fixed: No fixed version is explicitly recorded in the structured CVE data.
After
< 3.15.0 · Fixed: An authoritative update reference is available, but the fixed version is not recorded in the structured CVE fields. Check the linked vendor advisory for the applicable release.
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.
CVE-2026-15310: zipfile: bzip2/LZMA/Zstandard members decompress without a max_length bound, defeating chunked-read memory limits | BlackTree
