Use-after-free in "unicode_escape" decoder with error handler
There is an issue in CPython when using `bytes.decode("unicode_escape", error="ignore|replace")`. If you are not using the "unicode_escape" encoding or an error handler your usage is not affected. To work-around this issue you may stop using the error= handler and instead wrap the bytes.decode() call in a try-except catching the DecodeError.
- BDU:2025-10930
- ALSA-2025:23530
- DLA-4445-1
- openSUSE-SU-2025:15141-1
- openSUSE-SU-2025:15154-1
- openSUSE-SU-2025:15163-1
- openSUSE-SU-2025:15190-1
- openSUSE-SU-2025:15191-1
- openSUSE-SU-2025:15192-1
- RHSA-2025:23530
- RLSA-2025:23530
- SUSE-SU-2025:01877-1
- SUSE-SU-2025:02038-1
- SUSE-SU-2025:02047-1
- SUSE-SU-2025:02048-1
- SUSE-SU-2025:02049-1
- SUSE-SU-2025:02050-1
- SUSE-SU-2025:02057-1
- SUSE-SU-2025:02074-1
- SUSE-SU-2025:02297-1
- Published
- May 15, 2025
- Updated
- Jul 31, 2026
- EPSS
- 0.2% · 11th percentile
- CWE
- CWE-416
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Report tools
Action score
23
Monitor
Low priority for now.
- CVSS
- 23 / 40 · 5.9 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 0 / 30 · 0.2%
CISA SSVC decision
- Exploitation
- none
- Automatable
- no
- Technical impact
- partial
Vulnrichment: CISA's decision-tree inputs.
CNA vs NVD score
- NVD
- —
- CNA · PSF
- 5.9
- NVD has not scored this yet; the score shown is the CNA’s.
CVSS:4.0/AV:L/AC:H/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.
Noroxi analysis
No Noroxi analysis for this record yet
We don't hand-write analysis for the hundreds of thousands of vulnerabilities in the database; that wouldn't be honest. For notable, high-impact vulnerabilities our team writes the mechanism, detection and remediation steps.
We use this product, ask for helpAffected systems
—
Versions reported by the vendor
Affected version ranges reported by the assigning authority (PSF). Independent of NVD's CPE analysis and usually ahead of it.
Python Software Foundation CPython
- before 3.9.23affected · python
- 3.10.0 and later · before 3.10.18affected · python
- 3.11.0 and later · before 3.11.13affected · python
- 3.12.0 and later · before 3.12.11affected · python
- 3.13.0 and later · before 3.13.4affected · python
- 3.14.0a1 and later · before 3.14.0b2affected · python
Package-level exposure
OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| AlmaLinux:8 | python39 | before 3.9.25-2.module_el8.10.0+4083+53cad1fb | 3.9.25-2.module_el8.10.0+4083+53cad1fb |
| AlmaLinux:8 | python39-attrs | before 20.3.0-2.module_el8.6.0+2780+a40f65e1 | 20.3.0-2.module_el8.6.0+2780+a40f65e1 |
| AlmaLinux:8 | python39-cffi | before 1.14.3-2.module_el8.6.0+2780+a40f65e1 | 1.14.3-2.module_el8.6.0+2780+a40f65e1 |
| AlmaLinux:8 | python39-cffi | before 1.14.3-2.module_el8.6.0+3248+c431e88c | 1.14.3-2.module_el8.6.0+3248+c431e88c |
| AlmaLinux:8 | python39-chardet | before 3.0.4-19.module_el8.6.0+2780+a40f65e1 | 3.0.4-19.module_el8.6.0+2780+a40f65e1 |
| AlmaLinux:8 | python39-cryptography | before 3.3.1-3.module_el8.10.0+3765+2f9a457d | 3.3.1-3.module_el8.10.0+3765+2f9a457d |
| AlmaLinux:8 | python39-Cython | before 0.29.21-5.module_el8.6.0+2780+a40f65e1 | 0.29.21-5.module_el8.6.0+2780+a40f65e1 |
| AlmaLinux:8 | python39-Cython | before 0.29.21-5.module_el8.6.0+3248+c431e88c | 0.29.21-5.module_el8.6.0+3248+c431e88c |
| AlmaLinux:8 | python39-debug | before 3.9.25-2.module_el8.10.0+4083+53cad1fb | 3.9.25-2.module_el8.10.0+4083+53cad1fb |
| AlmaLinux:8 | python39-devel | before 3.9.25-2.module_el8.10.0+4083+53cad1fb | 3.9.25-2.module_el8.10.0+4083+53cad1fb |
| AlmaLinux:8 | python39-idle | before 3.9.25-2.module_el8.10.0+4083+53cad1fb | 3.9.25-2.module_el8.10.0+4083+53cad1fb |
| AlmaLinux:8 | python39-idna | before 2.10-4.module_el8.10.0+3849+a48d89aa | 2.10-4.module_el8.10.0+3849+a48d89aa |
| AlmaLinux:8 | python39-iniconfig | before 1.1.1-2.module_el8.6.0+2780+a40f65e1 | 1.1.1-2.module_el8.6.0+2780+a40f65e1 |
| AlmaLinux:8 | python39-libs | before 3.9.25-2.module_el8.10.0+4083+53cad1fb | 3.9.25-2.module_el8.10.0+4083+53cad1fb |
| AlmaLinux:8 | python39-lxml | before 4.6.5-1.module_el8.6.0+3248+c431e88c | 4.6.5-1.module_el8.6.0+3248+c431e88c |
| AlmaLinux:8 | python39-lxml | before 4.6.5-1.module_el8.6.0+2780+a40f65e1 | 4.6.5-1.module_el8.6.0+2780+a40f65e1 |
| AlmaLinux:8 | python39-mod_wsgi | before 4.7.1-7.module_el8.10.0+3989+a618fe15.1 | 4.7.1-7.module_el8.10.0+3989+a618fe15.1 |
| AlmaLinux:8 | python39-more-itertools | before 8.5.0-2.module_el8.6.0+2780+a40f65e1 | 8.5.0-2.module_el8.6.0+2780+a40f65e1 |
| AlmaLinux:8 | python39-numpy | before 1.19.4-3.module_el8.6.0+2780+a40f65e1 | 1.19.4-3.module_el8.6.0+2780+a40f65e1 |
| AlmaLinux:8 | python39-numpy | before 1.19.4-3.module_el8.6.0+3248+c431e88c | 1.19.4-3.module_el8.6.0+3248+c431e88c |
| AlmaLinux:8 | python39-numpy-doc | before 1.19.4-3.module_el8.6.0+2780+a40f65e1 | 1.19.4-3.module_el8.6.0+2780+a40f65e1 |
| AlmaLinux:8 | python39-numpy-f2py | before 1.19.4-3.module_el8.6.0+3248+c431e88c | 1.19.4-3.module_el8.6.0+3248+c431e88c |
| AlmaLinux:8 | python39-numpy-f2py | before 1.19.4-3.module_el8.6.0+2780+a40f65e1 | 1.19.4-3.module_el8.6.0+2780+a40f65e1 |
| AlmaLinux:8 | python39-packaging | before 20.4-4.module_el8.6.0+2780+a40f65e1 | 20.4-4.module_el8.6.0+2780+a40f65e1 |
+96
Same product
python software foundation: all recordsOther highest-scoring records for the same primary product.
- CVE-2025-4517Arbitrary writes via tarfile realpath overflow37Monitor
- CVE-2026-19445Use-after-free of a server-side SSLContext when sni_callback switches contexts36Monitor
- CVE-2026-6100Use-after-free in lzma.LZMADecompressor, bz2.BZ2Decompressor, and gzip.GzipFile after re-use under memory pressure36Monitor
- CVE-2026-3298Out-of-bounds write in Windows asyncio.ProacterEventLoop.sock_recvfrom_into() when using nbytes35Monitor
- CVE-2024-12254Unbounded memory buffering in SelectorSocketTransport.writelines()35Monitor
- CVE-2024-8088Infinite loop when iterating over zip archive entry names from zipfile.Path34Monitor
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
| Product / package | Fixed version | Source |
|---|---|---|
| Python Software Foundation CPython | 3.10.18 | Vendor (CNA) |
| Python Software Foundation CPython | 3.11.13 | Vendor (CNA) |
| Python Software Foundation CPython | 3.12.11 | Vendor (CNA) |
| Python Software Foundation CPython | 3.13.4 | Vendor (CNA) |
| Python Software Foundation CPython | 3.14.0b2 | Vendor (CNA) |
| Python Software Foundation CPython | 3.9.23 | Vendor (CNA) |
| almalinux:python39 | 3.9.25-2.module_el8.10.0+4083+53cad1fb · AlmaLinux:8 | Package registry (OSV) |
| almalinux:python39-attrs | 20.3.0-2.module_el8.6.0+2780+a40f65e1 · AlmaLinux:8 | Package registry (OSV) |
| almalinux:python39-cffi | 1.14.3-2.module_el8.6.0+2780+a40f65e1 · AlmaLinux:8 | Package registry (OSV) |
| almalinux:python39-chardet | 3.0.4-19.module_el8.6.0+2780+a40f65e1 · AlmaLinux:8 | Package registry (OSV) |
| almalinux:python39-cryptography | 3.3.1-3.module_el8.10.0+3765+2f9a457d · AlmaLinux:8 | Package registry (OSV) |
| almalinux:python39-Cython | 0.29.21-5.module_el8.6.0+2780+a40f65e1 · AlmaLinux:8 | Package registry (OSV) |
| almalinux:python39-debug | 3.9.25-2.module_el8.10.0+4083+53cad1fb · AlmaLinux:8 | Package registry (OSV) |
| almalinux:python39-devel | 3.9.25-2.module_el8.10.0+4083+53cad1fb · AlmaLinux:8 | Package registry (OSV) |
| almalinux:python39-idle | 3.9.25-2.module_el8.10.0+4083+53cad1fb · AlmaLinux:8 | Package registry (OSV) |
| almalinux:python39-idna | 2.10-4.module_el8.10.0+3849+a48d89aa · AlmaLinux:8 | Package registry (OSV) |
| almalinux:python39-iniconfig | 1.1.1-2.module_el8.6.0+2780+a40f65e1 · AlmaLinux:8 | Package registry (OSV) |
| almalinux:python39-PyMySQL | 0.10.1-2.module_el8.6.0+2780+a40f65e1 · AlmaLinux:8 | Package registry (OSV) |
| alpine:python3 | 3.11.12-r1 · Alpine:v3.18 | Package registry (OSV) |
| debian:python3.11 | 3.11.2-6+deb12u7 · Debian:12 | Package registry (OSV) |
| debian:python3.13 | 3.13.3-4 · Debian:13 | Package registry (OSV) |
| debian:python3.9 | 3.9.2-1+deb11u4 · Debian:11 | Package registry (OSV) |
| opensuse:python310 | 3.10.18-150400.4.82.1 · openSUSE:Leap 15.6 | Package registry (OSV) |
| opensuse:python310-core | 3.10.18-150400.4.82.1 · openSUSE:Leap 15.6 | Package registry (OSV) |
| opensuse:python310-documentation | 3.10.18-150400.4.82.1 · openSUSE:Leap 15.6 | Package registry (OSV) |
| opensuse:python312 | 3.12.11-150600.3.30.1 · openSUSE:Leap 15.6 | Package registry (OSV) |
| opensuse:python312-core | 3.12.11-150600.3.30.1 · openSUSE:Leap 15.6 | Package registry (OSV) |
| opensuse:python312-documentation | 3.12.11-150600.3.30.1 · openSUSE:Leap 15.6 | Package registry (OSV) |
| red hat:mod_wsgi | 0:4.7.1-7.module+el8.10.0+23075+0aa18782.1 · Red Hat:enterprise_linux:8::appstream | Package registry (OSV) |
| red hat:numpy | 0:1.19.4-3.module+el8.9.0+19644+d68f775d · Red Hat:enterprise_linux:8::appstream | Package registry (OSV) |
+30
Exploit status
No known public exploit
No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.
Research context
For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.
Timeline
From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.
No dated events beyond publication.
FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).
Patch and commit links
Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.
Credits
All researchersFinders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.
No credits in the CNA record.
Variant candidates
Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.
- CVE-2026-6100333 days apartUse-after-free in lzma.LZMADecompressor, bz2.BZ2Decompressor, and gzip.GzipFile after re-use under memory pressure36Monitor
- CVE-2026-19445503 days apartUse-after-free of a server-side SSLContext when sni_callback switches contexts36Monitor
Chain candidates
An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.
—
Bug bounty scope
No known public program.
Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).
Technical details
Attack conditions
- Someone with local access to the system can trigger it.
- No account or password is required.
- No user action is required.
- Special conditions such as timing or configuration are required.
If successful
- Confidentiality
- Integrity
- Availability
- Attack vector
- Local
- Attack complexity
- High
- Privileges required
- None
- User interaction
- None
- Scope
- X
Weakness class (CWE)
CWE-416 · Use After FreeCVSS vector
CVSS:4.0/AV:L/AC:H/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
nvd-secondary
Root cause
After a memory region is freed, another reference pointing to it is still used. By then, the same region may have been allocated for different data.
The bug in code
The whole CWE-416 classA representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.
Vulnerable
free(dev->buf);/* ... another thread is still running ... */process(dev->buf);Fixed
lock(&dev->lock);free(dev->buf);dev->buf = NULL;unlock(&dev->lock);Attack context
MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.
MITRE has no CAPEC/ATT&CK mapping for this CWE.
Change log
- Fix✗ → ✓
For records you follow, these changes also arrive as notifications. →
References
- github.com/python/cpython/commit/4398b788ffc1f954a2c552da285477d42a571292
- github.com/python/cpython/commit/6279eb8c076d89d3739a6edb393e43c7929b429d
- github.com/python/cpython/commit/69b4387f78f413e8c47572a85b3478c47eba8142
- github.com/python/cpython/commit/73b3040f592436385007918887b7e2132aa8431f
- github.com/python/cpython/commit/8d35fd1b34935221aff23a1ab69a429dd156be77
- github.com/python/cpython/commit/9f69a58623bd01349a18ba0c7a9cb1dad6a51e8e
- github.com/python/cpython/commit/ab9893c40609935e0d40a6d2a7307ea51aec598b
- github.com/python/cpython/issues/133767
- github.com/python/cpython/pull/129648
- mail.python.org/archives/list/security-announce@python.org/thread/L75IPBBTSCYEF56I2M4KIW353BB3AY74/
- www.openwall.com/lists/oss-security/2025/05/16/4
- www.openwall.com/lists/oss-security/2025/05/19/1
Vendor advisories and official records. Exploit/PoC links are deliberately left out.