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

CVE-2026-34355

CVE-2026-34355

Description

A buffer overflow in Apache HTTP Server's mod_proxy_html module (2.4.67 and earlier) can be exploited by an untrusted backend.

AI Insight

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

A buffer overflow in Apache HTTP Server's mod_proxy_html module (2.4.67 and earlier) can be exploited by an untrusted backend.

Vulnerability

A buffer overflow vulnerability exists in the mod_proxy_html module of Apache HTTP Server. This issue affects versions 2.4.0 through 2.4.67. The vulnerability can be triggered by an untrusted backend server. [1]

Exploitation

An attacker controlling a backend server can exploit this vulnerability. By sending specially crafted data to the mod_proxy_html module, an attacker can trigger the buffer overflow. Further details on the exact exploitation steps are not yet disclosed in the available references. [1]

Impact

Successful exploitation of this buffer overflow vulnerability can lead to a crash of the affected Apache HTTP Server process. In some scenarios, buffer overflows can also lead to arbitrary code execution, though this specific impact is not 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. Users are recommended to upgrade to version 2.4.68 or later. [1]

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

2

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