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High severity7.5NVD Advisory· Published Jun 8, 2026· Updated Jun 8, 2026

CVE-2026-42536

CVE-2026-42536

Description

Apache HTTP Server 2.4.x through 2.4.67 is vulnerable to a heap-based buffer overflow in mod_xml2enc when processing untrusted XML content.

AI Insight

LLM-synthesized narrative grounded in this CVE's description and references.

Apache HTTP Server 2.4.x through 2.4.67 is vulnerable to a heap-based buffer overflow in mod_xml2enc when processing untrusted XML content.

Vulnerability

A heap-based buffer overflow vulnerability exists in Apache HTTP Server, specifically within the mod_xml2enc module and the xml2StartParse function, when processing untrusted XML content. This issue affects Apache HTTP Server versions from 2.4.0 through 2.4.67 [1].

Exploitation

An attacker can exploit this vulnerability by sending specially crafted XML content to the server. The vulnerability is triggered when the mod_xml2enc module attempts to parse this malicious content using the xml2StartParse function. No specific authentication or user interaction is mentioned as required for exploitation in the available references [1].

Impact

Successful exploitation of this heap-based buffer overflow vulnerability could lead to a crash of the Apache HTTP Server process, potentially resulting in a denial of service. In some heap overflow scenarios, it may also be possible for an attacker to achieve arbitrary code execution, though this is not explicitly detailed in the provided references [1].

Mitigation

Apache HTTP Server version 2.4.68, released on 2026-06-08, includes a fix for this vulnerability [1]. Users are strongly recommended to upgrade to version 2.4.68 or later to mitigate this risk.

References
  1. Apache HTTP Server 2.4 vulnerabilities

AI Insight generated on Jun 8, 2026. Synthesized from this CVE's description and the cited reference URLs; citations are validated against the source bundle.

Affected products

1

Patches

1
35c6e405390e

cookie reqest header counting (#324)

https://github.com/icing/mod_h2Stefan EissingMay 27, 2026via body-scan
commit
1 file changed · +4 −0
  • mod_http2/h2_util.c+4 −0 modified
    @@ -1708,6 +1708,8 @@ static apr_status_t req_add_header(apr_table_t *headers, apr_pool_t *pool,
              && !ap_cstr_casecmpn("cookie", (const char *)nv->name, nv->namelen)) {
         existing = apr_table_get(headers, "cookie");
         if (existing) {
+            if (!nv->valuelen)
+                return APR_SUCCESS;
             /* Cookie header come separately in HTTP/2, but need
              * to be merged by "; " (instead of default ", ")
              */
@@ -1719,6 +1721,8 @@ static apr_status_t req_add_header(apr_table_t *headers, apr_pool_t *pool,
             apr_table_setn(headers, "Cookie",
                            apr_psprintf(pool, "%s; %.*s", existing,
                                         (int)nv->valuelen, nv->value));
+            /* Treat the merge as an "add" to not escape LimitRequestFields */
+            *pwas_added = 1;
             return APR_SUCCESS;
         }
     }

Vulnerability mechanics

No source-code context for this CVE — mechanics is only generated when we can read the actual fix diff. Without that, the four sections (root cause, attack vector, affected code, fix) would be speculation rather than analysis.

References

1

News mentions

1