CVE catalog

CVE-2026-34873

An issue was discovered in Mbed TLS 3.5.0 through 4.0.0. Client impersonation can occur while resuming a TLS 1.3 session.

Severity: Critical · CVSS 10CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N
Published: Apr 1, 2026, 12:00:00 AM UTC
Source: [NVD] · [CVE record]
EPSS: 0.24% · Oct 25, 2026

An issue was discovered in Mbed TLS 3.5.0 through 4.0.0. Client impersonation can occur while resuming a TLS 1.3 session.

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	mbedtls	sid	`3.6.7-3`	fixed
Debian	mbedtls	forky	`3.6.7-3`	fixed
Debian	mbedtls	trixie	`3.6.6-0.1~deb13u1`	fixed
Debian	mbedtls	bookworm	`2.28.3-1`	vulnerable
Cpe	mbedtls	Not reported	Not reported	vulnerable
Cpe	mbed_tls	Not reported	`3.6.6`	fixed
Cpe	mbed_tls	Not reported	`4.1.0`	fixed

Fixed-version evidence

Distribution	Package	Type	Release	Fixed version	Urgency	Origin	Bugs
Debian	mbedtls	source	sid	`3.6.6-0.1`	not yet assigned	Not reported	[1132577]
Debian	mbedtls	source	forky	`3.6.6-0.1`	not yet assigned	Not reported	[1132577]
Debian	mbedtls	source	trixie	`3.6.6-0.1~deb13u1`	not yet assigned	Not reported	[1132577]
Debian	mbedtls	source	bookworm	`(unfixed)`	not yet assigned	Not reported	[1132577]
Cpe	mbed_tls	cpe	Not reported	`3.6.6`	Not reported	Not reported	Not reported
Cpe	mbed_tls	cpe	Not reported	`4.1.0`	Not reported	Not reported	Not reported

[Debian bug #1132577]

Notes

[bookworm] mbedtls: Minor issue

OpenFactory catalog packages

[Debian 12 (Bookworm)]

[libmbedcrypto7]Affected
Source package: [mbedtls]
Details (2)
- 2.28.3-1 · amd64 · bookworm
  Affected
  nvd · mbedtls · debian · bookworm; nvd · mbedtls · debian · 12
- 2.28.3-1 · arm64 · bookworm
  Affected
  nvd · mbedtls · debian · bookworm; nvd · mbedtls · debian · 12
[libmbedtls14]Affected
Source package: [mbedtls]
Details (2)
- 2.28.3-1 · amd64 · bookworm
  Affected
  nvd · mbedtls · debian · bookworm; nvd · mbedtls · debian · 12
- 2.28.3-1 · arm64 · bookworm
  Affected
  nvd · mbedtls · debian · bookworm; nvd · mbedtls · debian · 12
[libmbedtls-dev]Affected
Source package: [mbedtls]
Details (2)
- 2.28.3-1 · amd64 · bookworm
  Affected
  nvd · mbedtls · debian · bookworm; nvd · mbedtls · debian · 12
- 2.28.3-1 · arm64 · bookworm
  Affected
  nvd · mbedtls · debian · bookworm; nvd · mbedtls · debian · 12
[libmbedtls-doc]Affected
Source package: [mbedtls]
Details (2)
- 2.28.3-1 · all · bookworm
  Affected
  nvd · mbedtls · debian · bookworm; nvd · mbedtls · debian · 12
- 2.28.3-1 · all · bookworm
  Affected
  nvd · mbedtls · debian · bookworm; nvd · mbedtls · debian · 12
[libmbedx509-1]Affected
Source package: [mbedtls]
Details (2)
- 2.28.3-1 · amd64 · bookworm
  Affected
  nvd · mbedtls · debian · bookworm; nvd · mbedtls · debian · 12
- 2.28.3-1 · arm64 · bookworm
  Affected
  nvd · mbedtls · debian · bookworm; nvd · mbedtls · debian · 12

[Debian 13 (Trixie)]

[libmbedcrypto16]Affected
Source package: [mbedtls]
Details (2)
- 3.6.5-0.1~deb13u1 · amd64 · trixie
  Affected · Fixed: 3.6.6-0.1~deb13u1
  nvd · mbedtls · debian · 13
- 3.6.5-0.1~deb13u1 · arm64 · trixie
  Affected · Fixed: 3.6.6-0.1~deb13u1
  nvd · mbedtls · debian · 13
[libmbedtls21]Affected
Source package: [mbedtls]
Details (2)
- 3.6.5-0.1~deb13u1 · amd64 · trixie
  Affected · Fixed: 3.6.6-0.1~deb13u1
  nvd · mbedtls · debian · 13
- 3.6.5-0.1~deb13u1 · arm64 · trixie
  Affected · Fixed: 3.6.6-0.1~deb13u1
  nvd · mbedtls · debian · 13
[libmbedtls-dev]Affected
Source package: [mbedtls]
Details (2)
- 3.6.5-0.1~deb13u1 · amd64 · trixie
  Affected · Fixed: 3.6.6-0.1~deb13u1
  nvd · mbedtls · debian · 13
- 3.6.5-0.1~deb13u1 · arm64 · trixie
  Affected · Fixed: 3.6.6-0.1~deb13u1
  nvd · mbedtls · debian · 13
[libmbedtls-doc]Affected
Source package: [mbedtls]
Details (2)
- 3.6.5-0.1~deb13u1 · all · trixie
  Affected · Fixed: 3.6.6-0.1~deb13u1
  nvd · mbedtls · debian · 13
- 3.6.5-0.1~deb13u1 · all · trixie
  Affected · Fixed: 3.6.6-0.1~deb13u1
  nvd · mbedtls · debian · 13
[libmbedx509-7]Affected
Source package: [mbedtls]
Details (2)
- 3.6.5-0.1~deb13u1 · amd64 · trixie
  Affected · Fixed: 3.6.6-0.1~deb13u1
  nvd · mbedtls · debian · 13
- 3.6.5-0.1~deb13u1 · arm64 · trixie
  Affected · Fixed: 3.6.6-0.1~deb13u1
  nvd · mbedtls · debian · 13

Observed: Oct 23, 2026, 10:35:51 PM UTC

References

[Debian Security Tracker] · [FIRST EPSS] · [National Vulnerability Database (NVD)] · [OSV Package Vulnerability Database] · [Red Hat security advisories and VEX] · [SUSE security advisories and VEX]