SB20261001116 - Ubuntu update for expat

Description

This security bulletin contains information about 12 vulnerabilities.

1) Resource exhaustion (CVE-ID: CVE-2025-59375)

CWE-ID: CWE-400 - Resource exhaustion

CVSSv4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]

The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.

The vulnerability exists due to application does not properly control consumption of internal resources. A remote attacker can trigger large dynamic memory allocations via a small document and perform a denial of service (DoS) attack.

2) NULL Pointer Dereference (CVE-ID: CVE-2026-32776)

CWE-ID: CWE-476 - NULL Pointer Dereference

CVSSv4: 6.9 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N]

The vulnerability allows a remote attacker to cause a denial of service.

The vulnerability exists due to a NULL pointer dereference in the XML parser when processing malicious XML content with empty external parameter entity content. A remote attacker can send a specially crafted XML file to cause a denial of service.

3) Infinite loop (CVE-ID: CVE-2026-32777)

CWE-ID: CWE-835 - Loop with Unreachable Exit Condition ('Infinite Loop')

CVSSv4: 6.9 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N]

The vulnerability allows a remote attacker to cause a denial of service.

The vulnerability exists due to an infinite loop in the DTD content parser when processing a specially crafted XML file. A remote attacker can send a specially crafted request to cause a denial of service.

4) NULL pointer dereference (CVE-ID: CVE-2026-32778)

CWE-ID: CWE-476 - NULL Pointer Dereference

CVSSv4: 6.3 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N]

The vulnerability allows a remote attacker to cause a denial of service.

The vulnerability exists due to a NULL pointer dereference in the function setContext in libexpat when processing XML input under low-memory conditions. A remote attacker can send a specially crafted XML file to cause a denial of service.

Exploitation requires repeated processing of malicious input following an initial out-of-memory condition.

5) Inefficient algorithmic complexity (CVE-ID: CVE-2026-45186)

CWE-ID: CWE-407 - Inefficient Algorithmic Complexity

CVSSv4: 6.9 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N]

The vulnerability allows a remote attacker to perform a denial of service attack.

The vulnerability exists due to computational complexity of attribute name collision checks. A remote attacker can pass specially crafted XML input to the application and perform a denial of service attack.

6) Insufficient entropy (CVE-ID: CVE-2026-41080)

CWE-ID: CWE-331 - Insufficient Entropy

CVSSv4: 1.8 [CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:A/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N]

The vulnerability allows a remote attacker to perform a denial of service attack.

The vulnerability exists due to insufficient entropy. A remote attacker can supply a specially crafted XML document and flood hashes, leading to a denial of service condition. 

7) Protection mechanism failure (CVE-ID: CVE-2026-50219)

CWE-ID: CWE-693 - Protection Mechanism Failure

CVSSv4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]

The vulnerability allows a remote attacker to cause memory corruption.

The vulnerability exists due to missing control flow integrity checks in XML_GetBuffer, XML_Parse, XML_ParseBuffer, XML_ParserFree, and XML_ParserReset when these functions are called reentrantly from bindings or callbacks. A remote attacker can trigger unsafe parser API calls to cause memory corruption.

The issue is described as relevant to language bindings.

8) Protection mechanism failure (CVE-ID: CVE-2026-56412)

CWE-ID: CWE-693 - Protection Mechanism Failure

CVSSv4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]

The vulnerability allows a remote attacker to cause memory corruption.

The vulnerability exists due to missing control flow integrity checks in doCdataSection when handling XML_TOK_DATA_CHARS callbacks. A remote attacker can trigger unsafe handler calls to cause memory corruption.

This issue is described as a hole in the fix for CVE-2026-50219.

9) Integer overflow (CVE-ID: CVE-2026-56403)

CWE-ID: CWE-190 - Integer overflow

CVSSv4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]

The vulnerability allows a remote attacker to cause memory corruption.

The vulnerability exists due to an integer overflow in storeAtts when parsing XML attributes. A remote attacker can supply crafted XML input to cause memory corruption.

10) Integer overflow (CVE-ID: CVE-2026-56404)

CWE-ID: CWE-190 - Integer overflow

CVSSv4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]

The vulnerability allows a remote attacker to cause memory corruption.

The vulnerability exists due to an integer overflow in addBinding when processing XML data. A remote attacker can supply crafted XML input to cause memory corruption.

11) Integer overflow (CVE-ID: CVE-2026-56405)

CWE-ID: CWE-190 - Integer overflow

CVSSv4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]

The vulnerability allows a remote attacker to cause memory corruption.

The vulnerability exists due to an integer overflow in getAttributeId when parsing XML attributes. A remote attacker can supply crafted XML input to cause memory corruption.

12) Integer overflow (CVE-ID: CVE-2026-56408)

CWE-ID: CWE-190 - Integer overflow

CVSSv4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]

The vulnerability allows a remote attacker to cause memory corruption.

The vulnerability exists due to an integer overflow in copyString when copying string data. A remote attacker can supply crafted XML input to cause memory corruption.

Remediation

Install update from vendor's website.

References

• https://ubuntu.com/security/notices/USN-8790-1