SB2026091538 - Debian update for expat

Description

This security bulletin contains information about 21 vulnerabilities.

1) Out-of-bounds write (CVE-ID: CVE-2026-56132)

CWE-ID: CWE-787 - Out-of-bounds write

CVSSv4: 9.3 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N]

The vulnerability allows a remote attacker to cause memory corruption.

The vulnerability exists due to an out-of-bounds write in doProlog when processing scaffolding index data. A remote attacker can supply crafted XML input to cause memory corruption.

2) 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.

3) Integer overflow (CVE-ID: CVE-2026-56411)

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 xmlwf notation list allocation when allocating notation list memory. A remote attacker can supply crafted input to cause memory corruption.

This issue affects the xmlwf tool.

4) Integer overflow (CVE-ID: CVE-2026-56410)

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 xmlwf resolveSystemId when resolving system identifiers. A remote attacker can supply crafted input to cause memory corruption.

This issue affects the xmlwf tool.

5) Integer overflow (CVE-ID: CVE-2026-56409)

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 the xmlwf output path join logic when joining output paths. A remote attacker can supply crafted input to cause memory corruption.

This issue affects the xmlwf tool.

6) 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.

7) Integer overflow (CVE-ID: CVE-2026-56407)

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 textLen handling when parsing XML data. A remote attacker can supply crafted XML input to cause memory corruption.

8) Integer overflow (CVE-ID: CVE-2026-56406)

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 XML_ParseBuffer when parsing buffered XML input. A remote attacker can supply crafted XML input to cause memory corruption.

9) 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.

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-2026-56403)

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.

12) 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.

13) Protection mechanism failure (CVE-ID: CVE-2026-56131)

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_ResumeParser when it is called from a handler. A remote attacker can trigger a handler-driven call to XML_ResumeParser to cause memory corruption.

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

14) 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.

15) 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.

16) 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. 

17) 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.

18) 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.

19) 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.

20) Integer overflow (CVE-ID: CVE-2026-25210)

CWE-ID: CWE-190 - Integer overflow

CVSSv4: 9.3 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N]

The vulnerability allows a remote attacker to execute arbitrary code on the target system.

The vulnerability exists due to integer overflow within the doContent() function. A remote attacker can pass specially crafted XML data to the application, trigger integer overflow and execute arbitrary code on the target system.

Successful exploitation of this vulnerability may result in complete compromise of vulnerable system.

21) NULL pointer dereference (CVE-ID: CVE-2026-24515)

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 perform a denial of service (DoS) attack.

The vulnerability exists due to a NULL pointer dereference error in XML_ExternalEntityParserCreate. A remote attacker can pass specially crafted XML data to the application and perform a denial of service (DoS) attack.

Remediation

Install update from vendor's website.

References

• https://lists.debian.org/debian-security-announce/2026/msg00315.html