CVE-2015-7183

What it actually does

Integer overflow in PL_ARENA_ALLOCATE within NSPR allows out-of-bounds memory writes, resulting in heap corruption that can be leveraged for arbitrary code execution or denial of service.

Why it matters to the business

Remote attackers can fully compromise affected systems, exfiltrate data, install persistent malware, or disrupt operations across any product using the vulnerable NSS library.

How an attack unfolds

An attacker supplies a malicious payload over the network that reaches the vulnerable arena allocation routine inside NSPR; the integer overflow produces an undersized buffer, subsequent writes corrupt adjacent heap structures, and control flow is redirected to attacker-supplied code.

How to fix it

Upgrade Mozilla NSS to version 3.19.2.1 or 3.20.1 (or newer) and Firefox to 42.0 or ESR 38.4 (or newer); rebuild or redeploy any dependent products that statically link the vulnerable NSPR library.

How to confirm the fix worked

Confirm NSS version strings in installed binaries or package metadata match or exceed the fixed releases; perform regression testing with known triggering inputs if available.

Typical attack path

1. Deliver crafted input via network protocol or file format processed by NSS
2. Trigger integer overflow in PL_ARENA_ALLOCATE
3. Cause undersized allocation and subsequent heap overwrite
4. Hijack control flow or crash the process

How to detect it

Examine application crash logs and memory dumps for corruption patterns originating in NSPR arena allocation routines; correlate with inbound network sessions that target NSS-dependent services around the time of the anomaly.

What your security team should do

• Immediately inventory all systems using NSS or Firefox and schedule upgrades
• Block or monitor ingress of untrusted content that exercises NSS cryptographic or parsing paths until patched
• Review and retire any custom builds that embed older NSPR copies