The olm_session_describe function in Matrix libolm before 3.2.7 is vulnerable to a buffer overflow. The Olm session object represents a cryptographic channel between two parties. Therefore, its state is partially controllable by the remote party of the channel. Attackers can construct a crafted sequence of messages to manipulate the state of the receiver's session in such a way that, for some buffer sizes, a buffer overflow happens on a call to olm_session_describe. Furthermore, safe buffer sizes were undocumented. The overflow content is partially controllable by the attacker and limited to ASCII spaces and digits. The known affected products are Element Web And SchildiChat Web.
総合評価: CVE-2021-44538 は高リスク（65.8/100）。CVSS 深刻度は重大。悪用される可能性が高い（EPSS 1.92%、77 パーセンタイル） 推奨対応: 悪用可能性が高いため、影響範囲の確認と修補の優先付けを推奨します。
リスクは変動します。再評価に基づき、本ページの表示内容を更新しています。
EPSS は日次で悪用されやすさの相対度合いを推定します。パーセンタイルは採点済み CVE の中での相対位置（高いほど相対的に深刻）を示します。
| # | 日付 | 旧 EPSS スコア | 新 EPSS スコア | Δ（新 − 旧） |
|---|---|---|---|---|
| 1 | 2026-06-15 | 2.38% | 1.92% | -0.46% |
| 2 | 2026-05-26 | 1.42% | 2.38% | +0.96% |
| 3 | 2025-11-21 | — | 1.42% | — |
EPSS の全履歴 （全 19 件）
この CVE の CVSS 指標。
| ベーススコア | バージョン | 深刻度 | ベクトル | 悪用しやすさ | 影響 | スコアの出典 |
|---|---|---|---|---|---|---|
| 9.8 | 3.1 | CRITICAL |
|
3.9 | 5.9 | [email protected] |
| 7.5 | 2.0 | HIGH |
|
10.0 | 6.4 | [email protected] |
| vendor | priority | summary | link |
|---|---|---|---|
alpine
|
critical | CVE-2021-44538: 4 source package rows (element-web, olm, riot-web, thunderbird); 16 state rows across 7 repos (3.17-community, 3.18-community, 3.19-community, 3.20-community, 3.21-community, 3.22-community, edge-community); fixed 16, open 0. | https://security.alpinelinux.org/vuln/CVE-2021-44538 |
debian
|
not yet assigned | CVE-2021-44538 not yet assigned priority: Debian including 2 source packages (olm, thunderbird), 10 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 9, open 1. | https://security-tracker.debian.org/tracker/CVE-2021-44538 |
suse
|
high | — | https://www.suse.com/security/cve/CVE-2021-44538/ |
ubuntu
|
medium | CVE-2021-44538 medium priority: Ubuntu including 3 source packages (node-matrix-js-sdk, olm, thunderbird), 44 status rows across 15 suites (bionic, focal, hirsute, impish, jammy, kinetic, lunar, mantic, noble, oracular, plucky, questing, trusty, upstream, xenial): ignored 20, released 12, needs-triage 10, DNE 2. | https://ubuntu.com/security/CVE-2021-44538 |
| ベンダー | 製品 | バージョン | 生の CPE |
|---|---|---|---|
| matrix | element | < 1.9.7 | cpe:2.3:a:matrix:element:*:*:*:*:desktop:*:*:* |
| matrix | element | < 1.9.7 | cpe:2.3:a:matrix:element:*:*:*:*:web:*:*:* |
| matrix | javascript_sdk | >= 2.4.2, < 15.2.1 | cpe:2.3:a:matrix:javascript_sdk:*:*:*:*:*:*:*:* |
| matrix | olm | >= 3.1.4, < 3.2.8 | cpe:2.3:a:matrix:olm:*:*:*:*:*:*:*:* |
| schildi | schildichat | < 1.9.7-sc1 | cpe:2.3:a:schildi:schildichat:*:*:*:*:desktop:*:*:* |
| schildi | schildichat | < 1.9.7-sc1 | cpe:2.3:a:schildi:schildichat:*:*:*:*:web:*:*:* |
| cinny_project | cinny | < 1.6.0 | cpe:2.3:a:cinny_project:cinny:*:*:*:*:*:*:*:* |
| debian | debian_linux | 9.0 | cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:* |
| debian | debian_linux | 10.0 | cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:* |
| debian | debian_linux | 11.0 | cpe:2.3:o:debian:debian_linux:11.0:*:*:*:*:*:*:* |
| URL | タグ |
|---|---|
| https://gitlab.matrix.org/matrix-org/olm/-/tags | Product Third Party Advisory |
| https://lists.debian.org/debian-lts-announce/2022/01/msg00001.html | Mailing List Third Party Advisory |
| https://matrix.org/blog/2021/12/13/disclosure-buffer-overflow-in-libolm-and-matrix-js-sdk | Patch Vendor Advisory |
| https://www.debian.org/security/2022/dsa-5034 | Third Party Advisory |