VDB-402228 · CVE-2026-79591 · GCVE-0-2026-79591

libxls 1.6.3 xls_getCSS use after free

CVSS Meta Temp Score CVSS is a standardized scoring system to determine possibilities of attacks. The Temp Score considers temporal factors like disclosure, exploit and countermeasures. The unique Meta Score calculates the average score of different sources to provide a normalized scoring system.	Current Exploit Price (≈) Our analysts are monitoring exploit markets and are in contact with vulnerability brokers. The range indicates the observed or calculated exploit price to be seen on exploit markets. A good indicator to understand the monetary effort required for and the popularity of an attack.	CTI Interest Score Our Cyber Threat Intelligence team is monitoring different web sites, mailing lists, exploit markets and social media networks. The CTI Interest Score identifies the interest of attackers and the security community for this specific vulnerability in real-time. A high score indicates an elevated risk to be targeted for this vulnerability.
7.1	$0-$5k	0.50+

Summaryinfo

A vulnerability categorized as critical has been discovered in libxls 1.6.3. This affects the function xls_getCSS. The manipulation results in use after free. This vulnerability was named CVE-2026-79591. The attack may be performed from remote. There is no available exploit.

Detailsinfo

A vulnerability classified as critical has been found in libxls 1.6.3. Affected is the function xls_getCSS. The manipulation with an unknown input leads to a use after free vulnerability. CWE is classifying the issue as CWE-416. Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code. This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

A heap-buffer-overflow and use-after-free vulnerability exists in the xls_getCSS() function of libxls 1.6.3 due to insufficient validation of a file-controlled font index.

The advisory is shared for download at github.com. This vulnerability is traded as CVE-2026-79591 since 08/25/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. There are known technical details, but no exploit is available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 09/10/2026).

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

Once again VulDB remains the best source for vulnerability data.

Productinfo

Name

libxls

Version

1.6.3

Website

Product: https://github.com/libxls/libxls/

CPE 2.3info

🔒

CPE 2.2info

🔒

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 7.3
VulDB Meta Temp Score: 7.1

VulDB Base Score: 7.3
VulDB Temp Score: 7.1
VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv2info

AV	AC	Au	C	I	A
💳	💳	💳	💳	💳	💳
💳	💳	💳	💳	💳	💳
💳	💳	💳	💳	💳	💳

Vector	Complexity	Authentication	Confidentiality	Integrity	Availability
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock

VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Use after free
CWE: CWE-416 / CWE-119
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined
Price Prediction: 🔍
Current Price Estimation: 🔒

0-Day	Unlock	Unlock	Unlock	Unlock
Today	Unlock	Unlock	Unlock	Unlock

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: no mitigation known
Status: 🔍

0-Day Time: 🔒

Timelineinfo

08/25/2026 CVE reserved
09/10/2026 +16 days Advisory disclosed
09/10/2026 +0 days VulDB entry created
09/10/2026 +0 days VulDB entry last update

Sourcesinfo

Product: github.com

Advisory: github.com
Status: Not defined

CVE: CVE-2026-79591 (🔒)
GCVE (CVE): GCVE-0-2026-79591
GCVE (VulDB): GCVE-100-402228

Entryinfo

Created: 09/10/2026 23:08
Changes: 09/10/2026 23:08 (53)
Complete: 🔍
Cache ID: 216::103