CVE catalog

CVE-2025-12781

pypy3: CVE-2025-12781

Severity: Low · CVSS 3.3CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N
Published: Jan 21, 2026, 11:00:00 PM UTC
Source: [NVD] · [CVE record]
EPSS: 0.56% · Oct 22, 2026

When passing data to the b64decode(), standard_b64decode(), and urlsafe_b64decode() functions in the "base64" module the characters "+/" will always be accepted, regardless of the value of "altchars" parameter, typically used to establish an "alternative base64 alphabet" such as the URL safe alphabet. This behavior matches what is recommended in earlier base64 RFCs, but newer RFCs now recommend either dropping characters outside the specified base64 alphabet or raising an error. The old behavior has the possibility of causing data integrity issues. This behavior can only be insecure if your application uses an alternate base64 alphabet (without "+/"). If your application does not use the "altchars" parameter or the urlsafe_b64decode() function, then your application does not use an alternative base64 alphabet. The attached patches DOES NOT make the base64-decode behavior raise an error, as this would be a change in behavior and break existing programs. Instead, the patch deprecates the behavior which will be replaced with the newly recommended behavior in a future version of Python. Users are recommended to mitigate by verifying user-controlled inputs match the base64 alphabet they are expecting or verify that their application would not be affected if the b64decode() functions accepted "+" or "/" outside of altchars.

Vulnerable and fixed packages

Distribution-reported package versions and fixes. These do not depend on matching against the OpenFactory package catalog.

Distribution	Package	Release	Version	Status
Debian	pypy3	sid	`8.0.1+dfsg-1`	vulnerable
Debian	pypy3	forky	`8.0.1+dfsg-1`	vulnerable
Debian	pypy3	trixie	`7.3.19+dfsg-2`	vulnerable
Debian	pypy3	bookworm	`7.3.11+dfsg-2+deb12u3`	vulnerable
Debian	python3.11	bookworm	`3.11.2-6+deb12u8`	vulnerable
Debian	python3.11	bookworm-security	`3.11.2-6+deb12u9`	vulnerable
Opensuse	python314	tumbleweed	`3.14.3-1.1`	fixed
Opensuse	python315	tumbleweed	`3.15.0~a3-4.1`	fixed

Fixed-version evidence

Distribution	Package	Type	Release	Fixed version	Urgency	Origin	Bugs
Debian	pypy3	source	sid	`(unfixed)`	not yet assigned	Not reported	[1135117]
Debian	pypy3	source	forky	`(unfixed)`	not yet assigned	Not reported	[1135117]
Debian	pypy3	source	trixie	`(unfixed)`	not yet assigned	Not reported	[1135117]
Debian	pypy3	source	bookworm	`(unfixed)`	not yet assigned	Not reported	[1135117]
Debian	python3.11	source	bookworm	`(unfixed)`	not yet assigned	Not reported	Not reported
Opensuse	python314	rpm	tumbleweed	`3.14.3-1.1`	Not reported	OPENSUSE-SU-2026:10206-1	Not reported
Opensuse	python315	rpm	tumbleweed	`3.15.0~a3-4.1`	Not reported	OPENSUSE-SU-2026:10152-1	Not reported

[Debian bug #1135117]

Notes

[trixie] pypy3: Not backported to older Python releases due to compat concerns [bookworm] pypy3: Minor issue [bookworm] python3.11: Not backported to older Python releases due to compat concerns

OpenFactory catalog packages

[Debian 12 (Bookworm)]

[idle-python3.11]Affected
Source package: [python3.11]
Details (4)
- 3.11.2-6+deb12u8 · all · bookworm
  Affected
  dsa · python3.11 · debian · bookworm
- 3.11.2-6+deb12u8 · all · bookworm
  Affected
  dsa · python3.11 · debian · bookworm
- 3.11.2-6+deb12u3 · all · bookworm-security
  Affected
  dsa · python3.11 · debian · bookworm
- 3.11.2-6+deb12u3 · all · bookworm-security
  Affected
  dsa · python3.11 · debian · bookworm
[libpython3.11]Affected
Source package: [python3.11]
Details (4)
- 3.11.2-6+deb12u8 · amd64 · bookworm
  Affected
  dsa · python3.11 · debian · bookworm
- 3.11.2-6+deb12u8 · arm64 · bookworm
  Affected
  dsa · python3.11 · debian · bookworm
- 3.11.2-6+deb12u3 · amd64 · bookworm-security
  Affected
  dsa · python3.11 · debian · bookworm
- 3.11.2-6+deb12u3 · arm64 · bookworm-security
  Affected
  dsa · python3.11 · debian · bookworm
[libpython3.11-dbg]Affected
Source package: [python3.11]
Details (4)
- 3.11.2-6+deb12u8 · amd64 · bookworm
  Affected
  dsa · python3.11 · debian · bookworm
- 3.11.2-6+deb12u8 · arm64 · bookworm
  Affected
  dsa · python3.11 · debian · bookworm
- 3.11.2-6+deb12u3 · amd64 · bookworm-security
  Affected
  dsa · python3.11 · debian · bookworm
- 3.11.2-6+deb12u3 · arm64 · bookworm-security
  Affected
  dsa · python3.11 · debian · bookworm
[libpython3.11-dev]Affected
Source package: [python3.11]
Details (4)
- 3.11.2-6+deb12u8 · amd64 · bookworm
  Affected
  dsa · python3.11 · debian · bookworm
- 3.11.2-6+deb12u8 · arm64 · bookworm
  Affected
  dsa · python3.11 · debian · bookworm
- 3.11.2-6+deb12u3 · amd64 · bookworm-security
  Affected
  dsa · python3.11 · debian · bookworm
- 3.11.2-6+deb12u3 · arm64 · bookworm-security
  Affected
  dsa · python3.11 · debian · bookworm
[libpython3.11-minimal]Affected
Source package: [python3.11]
Details (4)
- 3.11.2-6+deb12u8 · amd64 · bookworm
  Affected
  dsa · python3.11 · debian · bookworm
- 3.11.2-6+deb12u8 · arm64 · bookworm
  Affected
  dsa · python3.11 · debian · bookworm
- 3.11.2-6+deb12u3 · amd64 · bookworm-security
  Affected
  dsa · python3.11 · debian · bookworm
- 3.11.2-6+deb12u3 · arm64 · bookworm-security
  Affected
  dsa · python3.11 · debian · bookworm
[libpython3.11-stdlib]Affected
Source package: [python3.11]
Details (4)
- 3.11.2-6+deb12u8 · amd64 · bookworm
  Affected
  dsa · python3.11 · debian · bookworm
- 3.11.2-6+deb12u8 · arm64 · bookworm
  Affected
  dsa · python3.11 · debian · bookworm
- 3.11.2-6+deb12u3 · amd64 · bookworm-security
  Affected
  dsa · python3.11 · debian · bookworm
- 3.11.2-6+deb12u3 · arm64 · bookworm-security
  Affected
  dsa · python3.11 · debian · bookworm
[libpython3.11-testsuite]Affected
Source package: [python3.11]
Details (4)
- 3.11.2-6+deb12u8 · all · bookworm
  Affected
  dsa · python3.11 · debian · bookworm
- 3.11.2-6+deb12u8 · all · bookworm
  Affected
  dsa · python3.11 · debian · bookworm
- 3.11.2-6+deb12u3 · all · bookworm-security
  Affected
  dsa · python3.11 · debian · bookworm
- 3.11.2-6+deb12u3 · all · bookworm-security
  Affected
  dsa · python3.11 · debian · bookworm
[pypy3]Affected
Details (2)
- 7.3.11+dfsg-2+deb12u3 · amd64 · bookworm
  Affected
  dsa · pypy3 · debian · bookworm
- 7.3.11+dfsg-2+deb12u3 · arm64 · bookworm
  Affected
  dsa · pypy3 · debian · bookworm
[pypy3-dev]Affected
Source package: [pypy3]
Details (2)
- 7.3.11+dfsg-2+deb12u3 · all · bookworm
  Affected
  dsa · pypy3 · debian · bookworm
- 7.3.11+dfsg-2+deb12u3 · all · bookworm
  Affected
  dsa · pypy3 · debian · bookworm
[pypy3-doc]Affected
Source package: [pypy3]
Details (2)
- 7.3.11+dfsg-2+deb12u3 · all · bookworm
  Affected
  dsa · pypy3 · debian · bookworm
- 7.3.11+dfsg-2+deb12u3 · all · bookworm
  Affected
  dsa · pypy3 · debian · bookworm
[pypy3-lib]Affected
Source package: [pypy3]
Details (2)
- 7.3.11+dfsg-2+deb12u3 · amd64 · bookworm
  Affected
  dsa · pypy3 · debian · bookworm
- 7.3.11+dfsg-2+deb12u3 · arm64 · bookworm
  Affected
  dsa · pypy3 · debian · bookworm
[pypy3-lib-testsuite]Affected
Source package: [pypy3]
Details (2)
- 7.3.11+dfsg-2+deb12u3 · all · bookworm
  Affected
  dsa · pypy3 · debian · bookworm
- 7.3.11+dfsg-2+deb12u3 · all · bookworm
  Affected
  dsa · pypy3 · debian · bookworm
[pypy3-tk]Affected
Source package: [pypy3]
Details (2)
- 7.3.11+dfsg-2+deb12u3 · amd64 · bookworm
  Affected
  dsa · pypy3 · debian · bookworm
- 7.3.11+dfsg-2+deb12u3 · arm64 · bookworm
  Affected
  dsa · pypy3 · debian · bookworm
[pypy3-venv]Affected
Source package: [pypy3]
Details (2)
- 7.3.11+dfsg-2+deb12u3 · all · bookworm
  Affected
  dsa · pypy3 · debian · bookworm
- 7.3.11+dfsg-2+deb12u3 · all · bookworm
  Affected
  dsa · pypy3 · debian · bookworm
[python3.11]Affected
Details (4)
- 3.11.2-6+deb12u8 · amd64 · bookworm
  Affected
  dsa · python3.11 · debian · bookworm
- 3.11.2-6+deb12u8 · arm64 · bookworm
  Affected
  dsa · python3.11 · debian · bookworm
- 3.11.2-6+deb12u3 · amd64 · bookworm-security
  Affected
  dsa · python3.11 · debian · bookworm
- 3.11.2-6+deb12u3 · arm64 · bookworm-security
  Affected
  dsa · python3.11 · debian · bookworm
[python3.11-dbg]Affected
Source package: [python3.11]
Details (4)
- 3.11.2-6+deb12u8 · amd64 · bookworm
  Affected
  dsa · python3.11 · debian · bookworm
- 3.11.2-6+deb12u8 · arm64 · bookworm
  Affected
  dsa · python3.11 · debian · bookworm
- 3.11.2-6+deb12u3 · amd64 · bookworm-security
  Affected
  dsa · python3.11 · debian · bookworm
- 3.11.2-6+deb12u3 · arm64 · bookworm-security
  Affected
  dsa · python3.11 · debian · bookworm
[python3.11-dev]Affected
Source package: [python3.11]
Details (4)
- 3.11.2-6+deb12u8 · amd64 · bookworm
  Affected
  dsa · python3.11 · debian · bookworm
- 3.11.2-6+deb12u8 · arm64 · bookworm
  Affected
  dsa · python3.11 · debian · bookworm
- 3.11.2-6+deb12u3 · amd64 · bookworm-security
  Affected
  dsa · python3.11 · debian · bookworm
- 3.11.2-6+deb12u3 · arm64 · bookworm-security
  Affected
  dsa · python3.11 · debian · bookworm
[python3.11-doc]Affected
Source package: [python3.11]
Details (4)
- 3.11.2-6+deb12u8 · all · bookworm
  Affected
  dsa · python3.11 · debian · bookworm
- 3.11.2-6+deb12u8 · all · bookworm
  Affected
  dsa · python3.11 · debian · bookworm
- 3.11.2-6+deb12u3 · all · bookworm-security
  Affected
  dsa · python3.11 · debian · bookworm
- 3.11.2-6+deb12u3 · all · bookworm-security
  Affected
  dsa · python3.11 · debian · bookworm
[python3.11-examples]Affected
Source package: [python3.11]
Details (4)
- 3.11.2-6+deb12u8 · all · bookworm
  Affected
  dsa · python3.11 · debian · bookworm
- 3.11.2-6+deb12u8 · all · bookworm
  Affected
  dsa · python3.11 · debian · bookworm
- 3.11.2-6+deb12u3 · all · bookworm-security
  Affected
  dsa · python3.11 · debian · bookworm
- 3.11.2-6+deb12u3 · all · bookworm-security
  Affected
  dsa · python3.11 · debian · bookworm
[python3.11-full]Affected
Source package: [python3.11]
Details (4)
- 3.11.2-6+deb12u8 · amd64 · bookworm
  Affected
  dsa · python3.11 · debian · bookworm
- 3.11.2-6+deb12u8 · arm64 · bookworm
  Affected
  dsa · python3.11 · debian · bookworm
- 3.11.2-6+deb12u3 · amd64 · bookworm-security
  Affected
  dsa · python3.11 · debian · bookworm
- 3.11.2-6+deb12u3 · arm64 · bookworm-security
  Affected
  dsa · python3.11 · debian · bookworm

Next results

Observed: Oct 24, 2026, 2:00:28 AM UTC

References

[CERT-Bund public advisories] · [Debian Security Tracker] · [FIRST EPSS] · [OSV Package Vulnerability Database] · [SUSE security advisories and VEX]