CVE-2021-25636 [High] | Security Vulnerability in Libreoffice

LibreOffice supports digital signatures of ODF documents and macros within documents, presenting visual aids that no alteration of the document occurred since the last signing and that the signature is valid. An Improper Certificate Validation vulnerability in LibreOffice allowed an attacker to create a digitally signed ODF document, by manipulating the documentsignatures.xml or macrosignatures.xml stream within the document to contain both "X509Data" and "KeyValue" children of the "KeyInfo" tag, which when opened caused LibreOffice to verify using the "KeyValue" but to report verification with the unrelated "X509Data" value. This issue affects: The Document Foundation LibreOffice 7.2 versions prior to 7.2.5.

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2025-11-21	0.06%	0.20%	+0.14%
2	2025-11-18	0.16%	0.06%	-0.10%
3	2025-07-16	—	0.16%	—

Date

Old EPSS score

New EPSS score

Delta (New - Old)

2025-11-21

0.06%

0.20%

+0.14%

2025-11-18

0.16%

0.06%

-0.10%

2025-07-16

—

0.16%

—

Base score	Version	Severity	Vector	Exploitability	Impact	Score source
7.5	3.1	HIGH	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N` Click to expand Attack vector (AV:N) Could be attacked over the internet or any normal routed network—not just someone sitting at the machine. Attack complexity (AC:L) Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup. Privileges required (PR:N) No account or special rights needed—anonymous or random user is enough. User interaction (UI:N) Nobody has to click “OK” or open a trap file; it can work without a victim helping. Scope (S:U) Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems. Confidentiality (C:N) Doesn’t really leak secrets in a meaningful way. Integrity (I:H) They could widely tamper with or forge data—trust in the data is badly hurt. Availability (A:N) Service keeps running; no real outage angle.	3.9	3.6	[email protected]
5.0	2.0	MEDIUM	`AV:N/AC:L/Au:N/C:N/I:P/A:N` Click to expand Access vector (AV:N) Can be exploited remotely over network reachability. Access complexity (AC:L) Exploitation conditions are straightforward and predictable. Authentication (AU:N) No authentication is required. Confidentiality impact (C:N) No confidentiality impact. Integrity impact (I:P) Partial integrity impact. Availability impact (A:N) No availability impact.	10.0	2.9	[email protected]

Base score

Version

Severity

Vector

Exploitability

Impact

Score source

7.5

3.1

HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N Click to expand

Attack vector (AV:N): Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L): Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N): No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N): Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U): Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N): Doesn’t really leak secrets in a meaningful way.
Integrity (I:H): They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:N): Service keeps running; no real outage angle.

3.9

3.6

[email protected]

5.0

2.0

MEDIUM

AV:N/AC:L/Au:N/C:N/I:P/A:N Click to expand

Access vector (AV:N): Can be exploited remotely over network reachability.
Access complexity (AC:L): Exploitation conditions are straightforward and predictable.
Authentication (AU:N): No authentication is required.
Confidentiality impact (C:N): No confidentiality impact.
Integrity impact (I:P): Partial integrity impact.
Availability impact (A:N): No availability impact.

10.0

2.9

[email protected]

OS Trackers for CVE-2021-25636

vendor	priority	summary	link
`alpine`	high	CVE-2021-25636: 1 source package rows (libreoffice); 9 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 7, open 2.	https://security.alpinelinux.org/vuln/CVE-2021-25636
`debian`	not yet assigned	CVE-2021-25636 not yet assigned priority: Debian including 1 source packages (libreoffice), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5.	https://security-tracker.debian.org/tracker/CVE-2021-25636
`redhat`	medium	—	https://access.redhat.com/security/cve/CVE-2021-25636
`suse`	medium	—	https://www.suse.com/security/cve/CVE-2021-25636/
`ubuntu`	medium	CVE-2021-25636 medium priority: Ubuntu including 1 source packages (libreoffice), 9 status rows across 9 suites (bionic, focal, impish, jammy, kinetic, lunar, trusty, upstream, xenial): released 4, not-affected 3, ignored 2.	https://ubuntu.com/security/CVE-2021-25636

Affected software / configurations for CVE-2021-25636

Vendor	Product	Version	Raw CPE
libreoffice	libreoffice	>= 7.2.0, < 7.2.5	cpe:2.3:a:libreoffice:libreoffice::::::::
fedoraproject	fedora	34	cpe:2.3:o:fedoraproject:fedora:34:::::::*

References for CVE-2021-25636

URL	Tags
https://lists.debian.org/debian-lts-announce/2023/03/msg00022.html
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/NE6UIBCPZWRBWPSEGJOPNWPPT3CCMVH2/
https://www.libreoffice.org/about-us/security/advisories/CVE-2021-25636/	Vendor Advisory

URL

CVE-2021-25636 | Incorrect trust validation of signature with ambiguous KeyInfo children

Exploit prediction scoring system (EPSS) score for CVE-2021-25636

Common vulnerability scoring system (CVSS) metrics for CVE-2021-25636

Weakness enumeration for CVE-2021-25636

OS Trackers for CVE-2021-25636

Affected software / configurations for CVE-2021-25636

References for CVE-2021-25636