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Vulnerability details: VCID-eyxt-ja7f-c7gg
Vulnerability ID VCID-eyxt-ja7f-c7gg
Aliases CVE-2021-34813
Summary Matrix libolm before 3.2.3 allows a malicious Matrix homeserver to crash a client (while it is attempting to retrieve an Olm encrypted room key backup from the homeserver) because olm_pk_decrypt has a stack-based buffer overflow. Remote code execution might be possible for some nonstandard build configurations.
Status Published
Exploitability 0.5
Weighted Severity 8.8
Risk 4.4
Affected and Fixed Packages Package Details
Weaknesses (1)
CWE-787 Out-of-bounds Write
System Score Found at
epss 0.04458 https://api.first.org/data/v1/epss?cve=CVE-2021-34813
epss 0.04458 https://api.first.org/data/v1/epss?cve=CVE-2021-34813
epss 0.04458 https://api.first.org/data/v1/epss?cve=CVE-2021-34813
epss 0.04458 https://api.first.org/data/v1/epss?cve=CVE-2021-34813
epss 0.04458 https://api.first.org/data/v1/epss?cve=CVE-2021-34813
epss 0.04458 https://api.first.org/data/v1/epss?cve=CVE-2021-34813
epss 0.04458 https://api.first.org/data/v1/epss?cve=CVE-2021-34813
epss 0.04458 https://api.first.org/data/v1/epss?cve=CVE-2021-34813
epss 0.04458 https://api.first.org/data/v1/epss?cve=CVE-2021-34813
epss 0.04458 https://api.first.org/data/v1/epss?cve=CVE-2021-34813
epss 0.04458 https://api.first.org/data/v1/epss?cve=CVE-2021-34813
epss 0.04458 https://api.first.org/data/v1/epss?cve=CVE-2021-34813
epss 0.04458 https://api.first.org/data/v1/epss?cve=CVE-2021-34813
cvssv2 7.5 https://nvd.nist.gov/vuln/detail/CVE-2021-34813
cvssv3.1 9.8 https://nvd.nist.gov/vuln/detail/CVE-2021-34813
archlinux Low https://security.archlinux.org/AVG-2077
Reference id Reference type URL
https://api.first.org/data/v1/epss?cve=CVE-2021-34813
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-34813
https://gitlab.matrix.org/matrix-org/olm/-/commit/ccc0d122ee1b4d5e5ca4ec1432086be17d5f901b
https://gitlab.matrix.org/matrix-org/olm/-/releases/3.2.3
https://matrix.org/blog/2021/06/14/adventures-in-fuzzing-libolm
989997 https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=989997
AVG-2077 https://security.archlinux.org/AVG-2077
cpe:2.3:a:matrix:olm:*:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:a:matrix:olm:*:*:*:*:*:*:*:*
CVE-2021-34813 https://nvd.nist.gov/vuln/detail/CVE-2021-34813
USN-USN-5194-1 https://usn.ubuntu.com/USN-5194-1/
No exploits are available.
Vector: AV:N/AC:L/Au:N/C:P/I:P/A:P Found at https://nvd.nist.gov/vuln/detail/CVE-2021-34813
Exploitability (E) Access Vector (AV) Access Complexity (AC) Authentication (Au) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

high

functional

unproven

proof_of_concept

not_defined

local

adjacent_network

network

high

medium

low

multiple

single

none

none

partial

complete

none

partial

complete

none

partial

complete
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H Found at https://nvd.nist.gov/vuln/detail/CVE-2021-34813
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Exploit Prediction Scoring System (EPSS)
Percentile 0.88634
EPSS Score 0.04458
Published At Aug. 6, 2025, 12:55 p.m.
Date Actor Action Source VulnerableCode Version
2025-07-31T08:44:16.541425+00:00 Ubuntu USN Importer Import https://usn.ubuntu.com/USN-5194-1/ 37.0.0